#### Transcripts

1. PhysicsCourseOnline: Are you interested in learning all about physics? Do you want to master the high school in AP curriculum? Whether you're a high school student or an entry level college student, this course is for you. Each syriza dresses every topic thoroughly with lessons, demonstrations, an example problems.
2. June 04 MC (A and B1) Part 1: All right, This is the Juno four Physics Regents exam. I'm dealing with Onley. Multiple choice in this video, there are videos for both the B two and C three response parts. I hope you check out for this because it's multiple choice. I'm not going to show all the work in painstakingly detailed, but I am going to show work because you should be showing work. The secret to be only get most physics problems done is simply to make a good knowns list, identify your equation, plugging unsolved or make a good diagram and said, I'm going to do that. I'm probably not going to go and show you every equation. How Teoh rearrange every equation, do all the calculus, etcetera. Um, gonna kind of say that stuff out loud. You should be doing that. Take your time. So so important to take your time. Also, most of these multiple choice problems, as is the case with a lot of regions exams There are chocked full of Mr X. Read every word. Every word is important. You might think or assume the problems asking something than what it really is. Okay, lets go through and start doing this so number one velocity is the speed as displacement is toe. What what is the ah scaler? Come Mom. Version of displacement. And that's to be distance choice number four number two on the diagram we have a result in vector are which diagram represents the pair of component vectors component vectors and be that would combine to form a resulting vector. Well, components always go tell the tip to create the resulting. So it starts at the tail of the first and finish that the tip of the last, sending the tip of the last specter to be here in the tail, the first to be here. And of course, it's the original vector is up into the left. So what would it be fair to assume that we have one vector toe left and the other vector that is up. Of course. Naturally, it's not drawn this way down here. So we're really still looking, though, for any pairing that has a vector point left any vector pointed right? Because if I break this up, see if I can and groupies? Yeah, I could really remember. Vectors can slide. They just can't rotator get bigger? So this is really more or less we're looking for, which is choice one. Number three. A person is standing on a bathroom scale in an elevator car. The scale reads air value greater than the way to the person. At rest, the elevator could be moving. How? Ah, first and foremost, constant speed will not be the answer. Because constant speed, you will feel the same as you as if you're not moving at all. In fact, if you were traveling at constant speed and you didn't feel the vibrations of the elevator or have any other visual or sensible cues, you'd have no way of knowing that you're even moving. So we're gonna get out of the constant speed ones next. It's really important. Just think about the physics, but more or less, think about yourself being an elevator. When do you feel heavier in an elevator? I'm gonna quickly drawn elevate. I'm gonna put a person here when the elevator is not moving or a constant velocity. The normal force acting the person is equal to the waste. They could feel the scene wait. But what happens when the normal force or the not the normal foresee excel the elevator starts to accelerate upward. Isn't it fair to assume that the ground is pushing more up into your body? Well, if you're getting pulled down by gravity and the ground is pushing up on you, won't you kind of feel like you're getting wedged a little bit sandwich a little bit? You will. You're gonna feel heavier any time that you're moving upward and accelerating, increasing in speed. There are other scenarios, but of the two here, you're gonna feel heavier when choice for also choice threes were you feel later. If you think about it, the elevator says accelerate below you. You are now. I could've followed the explosion to the gravity by any means. But you're gonna accelerate more down than you were in the first place that the ground is pushing less up on you. So you're gonna feel later. The feeling of weight always comes from the normal force itself. With the normal force increases, you feel heavier. The normal force decreases. You feel later. OK. Number four degrees below shows the path of an object after it was thrown. What happens? The objects acceleration as it travels from a to B. This is such a trap question. They always have some version of this. I don't care if it's asking about direction, of acceleration, of force or whatever. They're always gonna ask a similar question like this, and you got to recognize that this is an object in free fall. Even though it's moving forward, there's no force moving it left or right. Since it's in free fall, it is solely under the influence of gravity, and gravity will not change. Its could remain the same choice. Three. Number five We have a 50.2 kilogram red ball thrown horizontally at a speed of four meters per second from height of three meters. 8.4 kilogram ball is thrown or is only from the same honey at a speed of eight meters per second, compared to the time it takes the red ball to reach the ground the time it takes the Green Mile route. The ground is what another kind of trap question. Because they're making you think, 01 ball was traveling with a greater speed forward, so it must be in the air longer or shorter amount of time. So let me do my red ball. I've got some sort of velocity forward four meters per second. It's not cruising, but it's moving and we're gonna have a green ball that's also gonna be chucked forward from the same high. I put it on top of each other so you can see them. But they're really from the same height. And it's going eight meters per second. Were like, Oh, it must be in the air twice as long. Now it's crazy. I mean, think about that would mean literally if you're moving forward when you jump off of something, it take, you just have some sort of delay. And what, you're getting pulled down now They're both getting pulled down the same rate. They're both gonna have project emotion. The only difference is the green was gonna lay in further out, but they're both get the ground at the exact same time. That's projectile motion 101 Review it. Choice three. Okay, Number six. The acceleration due to gravity on the surface of Planet X's 19.6 meters per second squared for an object on the surface of this planet weighs 980. New ones was a mess. All right, well, excitation due to gravity, that's G So if we recall that Wait f g is equal to M G than Masses, the weight divided by G. A lot of kids could get this far. But for some reason they're trained in the thinking that G always needs to be 9.8. That is not true. That's the GM, the surface of Earth. The GM Planet X. They gave it to us. It's 19.6. Take that 9 80 Divide by 19.6 and you're gonna get choice for 900. No, you're not gonna get choice for you to get choice 1 50 kilograms. What's wrong with me? Seven. A basketball player jump straight up to grab a rebound. If she was in the year 4.8 seconds. How high does she jumped? I think about that. Basketball player jumped up to get the rebound, but she was in the air for pointing second set me. She went up and then down. It took 0.8 seconds. The time it took to get to the highest point here. That's only 0.4 seconds. I'm gonna treat that as my time. The time is 0.4 seconds. Not only that, because of her motion on the way up will be equal to emotion. On the way down, I'm gonna take the travelling route on the way down for simplicity sake because at that spot, I'm gonna say she fell for 0.4 seconds. Which means for initial velocity, zero just allows me to do some quick math. My acceleration due to gravity is still G, which is giving 9.81 meters per second squared on a treat down as positive. Something to worry about Pretty negative in D is when I'm looking for I'm gonna use the equation. D equals V I t plus 1/2 a t squared the zero. That's why I made it. Zero makes a nice and simple distances. Could be 1/2 of a t squared. Plug it and make sure you don't forget to square that tea and Onley square that t you will get an answer of choice 2.278 meters. All right, let's move on nor ate the force required to start an object sliding across the uniform Horizontal surface is large in the force required to keep the objects lenient. Constant velocity, the magnitudes of the required forces air different in these situations because the force of kinetic friction, what well, kinetic means moving and if it requires less effort to keep it moving than it did to get moving, that it should imply that the force of kinetic friction is less than the force of static friction. Eight. Choice to You also could probably confirm that by recalling that the coefficients of friction on the front page kinetic is always larger than aesthetic. Right back over to number nine. We have a 50 kilogramme student through a 500.4 kilogram ball with a speed of 20 meters per second. What was the magnitude of the impulse that student exerted on the ball? Okay, let's make sure that we would get with the mass of the students will say M sub passes 50 kilograms. The mass of the ball is your 0.4 kilograms through with a speed of 20 meters per second. That's the change and speed the ball. The ball started. Rest right. That's didn't give it that 20 meters of speeds and Delta V is 20 meters per second. We want on the matter to the impulse that this didn't examine the ball. What's J. impulse back page. Let's get to the mechanic section and we know impulse. And if you don't remember what Impulse stands for you look on the right impulses. Jay. I know it doesn't necessary very natural. And so we're gonna see here that j equals F T or Delta P on with the Delta P part down. Well, all right. Both Jay's F Net, Times Time or Delta P we're going to use in the Delta P because Delta P is changing momentum, which is mass times change of velocity. Here's the thing we're looking for. J is M Delta V. We're gonna use the impulse with student exerting the ball, which is really the impulse that the ball gains. So we use the balls mass 0.4 times. It's changed 20. And for number nine, you could get eight new in seconds. All right. 10. A man pushing a baby stroller compared to the magnitude the force exerted the stroller by the man the men into the forest Little with the man on the street. All I love these Don't you guys someone's? You know, Newton's third law. You know, it has to be the scene these air gimmes awesome. 11. The work done and moving a block across a rough surface and the heat energy gained by the rock by the blocks. Or it can both be measured in what will keep the work done. That's an energy unit. He energy unit even says heat energy, both energy. That's or jewels 12. Two weightlifters 11.5 meters tall, nearly 12 meters tall, raised identical 50 kilogram mass. Above their heads compare the work done by the weightlifter, who is 1.5 meters tall. The work done by the weight lifter is two meters. Tell us what work is changing energy. In this case, they're undergoing potential energy change, which is giving M G Delta H. Since they both are raising the same mass. Object G is the same for both, Really. The one that has the higher Delta H will be the greater energy. So compared to the work done by the weight lifter was 1.5. The one that is to is gonna do more work. Greater choice to move up. Top right corner 45 kilogram boy is writing a 15 kilogram bicycle with speed of eight meters per second whereas the combined cannot get into the boy in the bicycle. So the NASA the boy is gonna be 45 kilograms. The mass of the bike is 15 kilograms, and we know the speed is eight meters per second. We're looking for kinetic energy. Kinetic energy is 1/2 m v squared. Because we're looking for the combined energy of the two, we're gonna look at their combined mass. What's 1/2 of the two masses added together? 45 plus 15. Toss parentheses around. That's you. Do you calculated work properly? Times Ace eight squared. Go ahead, toss that in your calculator. You're gonna get 1920 jewels. Erase this work. By the way, if I'm going to quick, just pause it, rewind it. Whatever. 14 a five to enforce causes a spring to stretch 50.2 meters a five new enforce. And since it's a spring, it's a spring force. Because of the spring to stretch, that's X 50.2 meters. We want the potential energy stored in the spring. Gosh, this is another one of those misdirect once in one's one's making unknowns. This helps a lot because a lot of you come over here. You look at P e and you're all like Okay, 1/2 k x squared. It's Write that down. P E is one. You don't even write it down to just start tossing stuff in your calculator at this point, which is lazy. And it's why you get these wrong. Because if you notice here, you need cane out f magically somehow lost in his turn f in decay, and that is not gonna work. Instead, we get a look at the other force equation. F equals K X. We gotta solve for K first. So first job is a software K K will be equal to F over X tossed on your calculator. Five over point to that's 25 new ones per meter. Now toss it in the 1/2 k X squared. I'll do that. Work up here. So it's 1/2 of the 25 times the point to Mixture scoring on Lee. The point to if you did everything right here to get choice. 2.5 jewels are a number 15. A 40 kilograms student runs up a staircase to a floor that is five meters higher that her starting point in seven seconds. What's the power? Let's do this Secure. We got a mass is 40 kilograms. We know that there change in height of five meters and we know the time is seven seconds. We want no power. Powers would be work. Overtime work is changing energy over time. The change in energy of this students undergoing is potential energy. So, like an MG Delta H over time because they gave it to us. An m not wait. We do need. They multiply gravity and there's we have 40 times, 91 times five. The entire top turn divided by seven and you got to get choice to 280 wants 16. What type of field is present near moving electric charge Moving electric charge. Ah, this is one that is often overlooked in regions physics because it's rarely brought up. An electric charge will always have an electric field around it. Okay, so we have a negative charge here and say it's getting electric fields surrounding it. That's true, but the fact that it's moving there's another thing there, and that's the one thing you need to know about. Electromagnetism is a moving charge, will always creating magnetic field as well. This is known as electromagnetism. The answer is both an electric field and magnetic field. 17. A negatively charged plastic comb is brought close to but does not touch a small piece of paper. The common the paper attracted to each other. The charge on the paper has another one. A lot of students say Okay, they say Okay, find the comb is attracting the paper. That must mean that their opposite Lee charged Opposites attract. So if you say the plastic comas negative, that must mean the papers posit that is simply not true. Attraction does not necessarily indicate charge. You have to remember that neutral objects can be attracted. So the answer to this one and I'll just say it is either positive or neutral choice to let me try to explain why this is something that's not terribly hard, but often confusing. If I have a rod, that's negative. Electrons that are in that paper are gonna slightly rearrange himself ready at polarization . The electrons that are in the paper gonna move away from the electron on the road. So we're gonna get kind of ah clustering of electrons over here, leaving behind a positive region over here. But because charge never exchanged, this is still neutral. However, now we have a positive pole. We have a negative one near it. They're gonna track towards each other. 18 if a 1.5 volt cell is to be completely recharged, age electron must be supplied with the minimum energy of what? You know, energy problems are kind of silly, but the whole definition of an electron volt is the amount of energy to move an electron over one volt. Since we have 1.5 volts, the amount of and you're looking at is choice number one. Now, we could try to map this out if you really wanted to, but I think conceptually makes more sense. But ah, that would be V equals W over Cousteau. W equals v Times Q. So if we were to math it out, we would use the V of 1.5 times a charge of 1.6 times 10 minute of 19. But then that would get you your energy and jewels. Something with that divide the whole thing. By the conversion from Jules TV, which is 1.6 times in a name taken in a little bit about this whole thing cancels out. Leaving behind 1.5 e. V. Um, I like to think of it as a V is the energy to require moving charge over a certain number of voltage. Sensible to just 1.5 volts. It should be choice one. All right, Number 19. The current traveling from the cathode to a screen of a television picture tube is five by 10 in the negative five amps. How many electron? Strict The screen. Five seconds. We know this is current. I equals five by 10 of the five negative five amps. Make unknowns list. It helps. Time is equal to five seconds. What am I doing? Putting a question mark there. We want to know how many electrons that is. So the number of electrons interesting here. Um, if we go over to our tables, we get electricity. Section C equals I equals Q over tea so we can find the charge. So the charge is going to be I'd times T which is the five by 10 of the five Egat's medium eraser out here. Five were among here. I'm all over the map, right Delta Q is gonna be five by 10 in the negative five. That whole thing times five. Ah, that's gonna get us 25 by 10 in the negative five. That's not what we want, cause that's que we won't know the number of electrons owns confected from Page nam of ah, the Charge one electron which has one elementary charge Please understand the e stands for elementary charged on electron It is 1.6 times 10 in the negative 19. So we've got to take this whole thing once we know our charge and divide by that number Where to get traced three.
3. June 04 MC (A and B1) Part 2: Let's move on. Number 20. Moving electron is deflected by two opposite. We charge parallel plates showing the dagger in blue C D. The electric field between plates. Direct from what? What? Well, here we go with a negative charge. It's getting pulled up, which must mean see is positive. Must mean D is negative. Electric field always goes positive to negative, so it's going from C to D. Choice three 21. The diagram shows two identical metals metal metal spheres and be super by a distance. D Each sphere has mass m and possesses charge. Q. Which dagger on presents? Electrostatic foursome and the gravitational force acting on sphere be Do this fear? A Let's get gravity other way. All masses are always attractive. All masses are always attractive. The gravitational force act dance. Fear be will be towards fear A just like a will be towards be. Now let's get to the electrostatic. They're both positive. They're gonna repel each other like charges repel. So we're looking at one that has the gravitational force to the left and then the other one that has electric force to the right. Ah, golly! Gee, where am I? Here. I'm all over the place. Choice to 21 is choice to 22. Below list various characteristics of to Mattel acquires a n B F. Where a is resistance are and what would be his reason. Then wire be has resistance. What? Well, let's try to see the differences here. The materials the same. Which means the Rose. Let's get to the equation versus might Make more sense Articles row L over a rose detent dependent on the material. Since materials are the same, the rose will be the same. A has half the length is B, but B has twice the area, and since area is under the fraction increasing area causes the resistance to G O. Down. Increasing length causes the resistance to G O up. We increased one and decrease the other at the exact same factor, which means they should have a canceling effect. 22. The answer is Choice one. It is the same resistance. 23. The diagram below shows a an electric circuit consisting of a 12 volt battery, a three m resistor R one and any variable resistor arc to what value must have variable resistor be set to produce a current of one AM through our one so last. It's like what is variable resistant will think about it. Variable means that could various is simply just a resistor that you can change its value So we want. What value must that be to make our one's current Be one amp well, understood this a series circuits. So the current flowing through our one is the same as the current flowing through our two, which is everywhere. So if we know that V equals IR, I totals when I'm looking for that's V total over r e que When we Novi totals 12 volts So we want to know one equals 12 over necks R e Q. So my ar e que is 12/1 or 12 ohm since its Siri's ours add up, which means three plus what equals 12 9 homes Choice to All right, 24. Energy of a photon is inversely proportional to its want. This is where if we look in the energy of a photon modern section, we see here that it's HF which is h c. Overwhelmed. So inversely means if one goes up there that goes down, i e. What is under the fraction wavelength 25. The energy equivalent of a rest mass of an electron is approximately. What? Okay is can get kind of tricky. Well, let's figure this one out. We need the rest. Massive in electrons. Let's get over here. Rest mass. Um, electron 9.11 by 10 of the native 31 kilograms. We're looking at energy in jewels, so we can't use that a whole universal mass stuff. So we're probably going to think outside the box here, hopefully recall energy equivalence. Is that formula that famous dude with? I don't know, funny name Einstein or something like that? Yeah. It's the thing that he kind of is famous for. Ah, Where are we? Here? Bram E equals M. C squared. That's what we've gotta use. We no see, It's the speed of light. So it's gonna be those numbers plugged and make sure Onley squaring the three by 10 of the eight. The speed of light number 25. I'm not gonna write it all out and just get to know the answer choice to All right. 26. A single vibrate Ori disturbance. I e. A vibration movie through medium is called what? So I single disturbance? A single vibration, just one portion of maybe a consistent wave that's known as a pulse. Just that one little hump, Not an entire way that goes over and over and over again. That would be a periodic disturbance, not a single disturbance. 27. An electric bell connected to a battery is sealed inside a large jar. What happens is the heirs and move from the jar. Ah, can sound travel through air. NASA can't travels. We're looking for anything that says, Basically is sound disappears, Bubba. Bubba bells, loudness decreases called like that because the sound waves key travel through a vacuum. That's true twice for is the answer. Electric circuit has nothing to do with that, like from an integration totally can heard. 28 out. Be careful with this woman. Three. This real quick here sound. We have passes from water where the speed is given in to air. This be the way to speed man. When I first did this sq dollar because I was thinking this was a refraction was light traveling from one of the air speed up right? But it's not. This is sound. It's not refraction. it sound first and foremost every way. I don't care if it's later sound the frequency once That's the way it has been created. The frequency remains the same. Let's get rid of three and four. We just got determined we'll light will sound. I'm sorry. Well, sound trouble faster and water or air. And this is a council question. You're doing the no. We're gonna have our fastest in solids, then liquids and then slowest in gases. And this has to do with them. Molecular separation. The particles are further apart, and gas is that it takes longer for energy to travel through them. Hence, as we go from wave as we go from water to air, we're actually gonna slow down choice number one Which phenomena occurs when an object absorbs wave energy that matches the objects and natural frequency that is literally the definition of residence. If you don't understand this or don't know this better, write this one down because that is the definition of residents. 30 array of monochromatic light and air is incident an angle of 30 degrees on a boundary of corn oil. What is the angle of refraction to the nearest agree for this light ray. So a ray of light and air is incident at an angle of 30 degrees. That's my incident. Let's Fada one and we're traveling from one medium to the next. Let's write down my index. This is Ares index of refraction is one. Now it's getting. Then hit the boundary with corn oils. We know it's gonna have a different index. What? We think it's gonna have a different next. Let's look at her index of refraction. Let's get to be on the inside. Cover the front page towards the bottom right below the magnetic spectrum and corn oils indexes 147 So, yeah, it's definitely gonna change. So what's new? My new angle is it Snows law and one sign fatal one equals and to sign. Fated to. We're looking for theater, too. So let's go out and find Sign fated to first and then please make sure you inverse that. So we get n one sign theater one divided by and two and then we're gonna do the inverse Sinovel that plug and appropriately that we have here and we're gonna get for number 30 choice to 31. A wave is diffraction as it passes through an opening in a barrier. The men of the fraction the wave undergoes depends on both the what? To fraction moments that bending the wave as it goes to the barrier and that barrier size is definitely get affected. You resolve this stuff here anyhow, um, size of the openings get effective. But also the size of the wave itself needs to be affected. We really know the size of the thing going through the opening and the size of the opening itself. It's give me choice three 32 sound of waves. An observer are moving relative to each other. The observable detect a steadily increasing frequency is an interesting one. You gotta potentially is two words here. Okay, steadily increasing. So you're going to detect an increase in frequency if their relative distance between them is decreasing, so they're moving towards each other. So you're going to get increasing frequency if it's moving towards it. This is true, but that frequency will maintain a constant frequency at a higher level. So long as the velocity isn't changing. We want to have a read A list, steadily increasing frequency. So not only do we want to be higher, but we want to be higher and higher and higher and higher and higher, and we want to continue getting higher and higher and higher and higher. That doesn't mean they need to be accelerating towards each other so he can accept it toward the source. The source towards him won't really matter. 33 which diagram has both wavelength and amplitude labeled correctly wavelength is the length of the wave, which is the any time that point repeats itself. Amplitude is a distance. The wave portion is above the equilibrium line. In this case, equilibrium line is the dash lines. So too, is bad for amplitude. For is bad for amplitude one in three or both correct for amplitude. Let's get wavelength here. This is only half a wave. Here is a whole wave. Wavelength is the distance of one whole wave. It is Choice three 34. Laser beam is directed the surface of a smooth compound as represented diagram below which organisms could be eliminated by the laser late. Well, let's get the simple one. Either way, any time we have a surface light will reflect off of it, so these two angles will end up equaling each other so that this is possible that bird can be illuminated. Are we gonna get it so it stops and somehow turns this way. That would be where that would imply There's something here. There's no surface there, the normal. It's just a reference point so the crab won't be illuminated as we gotta determine well, that laser go unimpeded, or will it bend in the bends? If there is a different index, we're going from air to water. The index is different. We're going to get bending. Seaweed will not be eliminated. It's gonna be the bird and the fish choice one. All right. 35. Doctor blows show represents the waves of equal, empty and frequency pointing. Approaching Pia's. They go through same medium. If the two waves pass through each other. Ah, the meaning that point people do what? This is kind of tricky. It's does involve some spa. They show, um, skills. I'm going to redraw these so I can kind of move them. It will be a little easier to explain as long as their equal, which I'm not necessarily nailing, but whatever. So I'm gonna make it. So where the blue. Ah, trough. Okay, now the right one was also traveling at that spot. So it's Peak is there. So this is where they're on top of each other. These two guys, they're gonna cancel each other out. So at that point, he won't be doing anything now. They both moved the same time, so we'll stop moving blue separately from red. They're both completing the same number of the same amount of traveling here. Both equal liberalism top each other Piece still won't move now. Pique Piece Crest is on top of the reds trough. The blues crescent in the reds truck cancelling out. Still, it's good. Stay stationary. Ah, the answer is removed. Station. Another way of thinking about it is this is gonna be a standing wave to waves of equal amplitude and frequency approaching each other. That's a stating wave. This is gonna be a nude. It won't move
4. June 04 MC (A and B1) Part 3: 36 applied to an object for a period of time. Which graft best represents the acceleration, the object as the function is lapsed constant, unbalanced force. Unbalanced force means there's a net force. Net force equals M A. As long as the mass doesn't change, the A will be related to the F. It's constant, which means we will have a net force that stays the same the whole time. Which means a stays the same the whole time. It's an acceleration time graph for looking for the one that has a not changing, that is choice four 37. A graph below represents kinetic energy and gravitational potential energy and total mechanical energy of moving block, which describes the motion of the block. So what we see here is we see here it starts off with hike potential energy that decreases . And while that's decreasing, your kinetic energy is going up. But while that's happening, we see the mechanical energy staying the same, which means there will be no energy loss. It starts at a high P E, and then gains goes to a low p, which means it's heights changing, which means it must be falling and there is no friction or anything here religiously at free fall, that's all it is. Free fall. All right, So 38 diameter of us penny. Closest to what? Oh, student safeties. And rightfully so. They're confusing. And you think that these estimation ones mean you need to know exactly the size of a penny and you do not. The easiest way of doing these is eliminating the crazy wounds and thinking about what you have left. Just look at your answers and determine what did you see? How they're all factors of 10 apart, which means they're 10 times smaller than each other or 10 times larger in each other. I don't care how you want think about it, but they're 10 times apart from each other. So let's go through and think about what each of these mean and Alyssa. This is 10 to 0, which is a fancy way of saying one times 10 of the zero well, 10 and zero is one. So what's one times 11? This is one meter. This is one times 10 in the negative one or 10.1 meter. This is one times 10 to the negative two or 20.1 meter and then finally 0.1 meter a penny is obviously not a meter long. You should know that. Let's give it to this. Now. These three might start to trip you up a little bit. They probably shouldn't. We're looking at 1/10 of a meter, a centimeter or a millimeter, but let's think about this on the region's you get a ruler, you should be able to look right down in your ruler and say, Hey, what is 10 centimeters long? Look like cause choice to is 10 centimeters says it's 1/10 of a meter. Well, I mean, depending on the device you're looking at with me, you probably will agree that that's close to 10 centimeters long, more or less. I mean, if you're looking at this with a phone or something might seem smaller, but it is not small. 10 centimeters is significantly larger than a penny. Scared of that? Now, again, kind of looking at your ruler here. Think about it. 1/10 of 10 centimeters, which is 100.1 meters, which would mean it's one centimeter. Isn't it fair to assume that a penny's probably about one centimeter long in diameter. Yes, it's gonna be. This is my answer. It's not a millimeter. A millimeter is really, really tiny. It's really, really smaller. Is that one line? The tiniest line on the ruler? No. Okay, Choice three. Try not to overcomplicate it. Just think about what you got and go from there. All right? 39 of 40 were dealing with the TAT data table here, Dad Table lists the energy and correspondent frequencies of five photons in which part of regimented expecting with photons d be found for this. We just got a look at the frequency to buy 10 of the 13. The EM spectrum lays it out in terms of frequency. Where are we? Let's go up a little bit. Here we go. What did I just say? 10 of the 13. 10 of the 15. 10 of 13. So frequencies the bottom number. Make sure you see that here. 10 of the 13. Let's look up here. We're dealing with infrared choice one. 40. The graph below represents the relationship between the energy and the frequency of photons . What's the slope could represent? Well, you can determine the slope of anything by running its variable in the why or the variable in the X. We're looking at what is e over f equal. A lot of times you need the hunt around, but you can probably recall that we're dealing with frequency of photons and energy, which is all modern physics. Let's get their modern physics is halfway through this page, but profitable for e equals HF Eat of auto by after for his H H is Planck's constant. The slope of this graph represents Plank's constant, which you can find the front page of the tables. I know it's 6.63 times 10 to the negative for negative 34 jewel seconds. All right, which combination of quirks could produce a neutral berry on? You know, these standard particle ones? They're so simple. As long as you don't get bogged down by the confusion. What's a quirk? What's a Barry and blah, blah, blah, blah? Let's get to the standard model standard model part of our reference tables, which is going to be on the bottom half of this page, and we're looking at a neutral berry on Well, you need to know that means all barriers must be three cork so which combination of corks can add up to zero. There's a bunch of different ones here, so I should probably just go through each one. C d t. Let's see. Ah, 2/3 plus 2/3 minus 1/3. That will leave us with plus one. That's not the answer. C. T s 2/3 2 3rd minus that there is still plus one. That won't be the answer. C D B 2/3 negative. 1/3 negative. 1/3. Yet that gets us to 0 2/3 miles. 30 miles. 30 0 That is my answer. Do I know what particles C D B is? I have no idea nor to you and it doesn't matter. 42 through 44. The last set here, I think. No, I think there's another page. Sorry, 20 on resistant. A 30 ohm resistor connected in parallel to a 12 volt battery is shown and meters placed right here is showing. What is the equipment? Really? Resistance of the circuit. First and foremost, look at it, Recognize or read it. It's a parallel circuit. Equivalent Resistance for parallel circuits can be found in the electricity section. Let's go to parallel and we're dealing with out this fractional stuff. Okay, so we're looking at one over R E Q is equal to one over r one plus one over r two We know r one and R to so one over r e Q Just give you 1/20 plus 1/30. If you struggle with fractional Matthews, your calculator, you're gonna get well, I'm gonna go ahead and do the known calculator version 3 60 ifs plus 2/16 or 5/16. That is not the answer, because that's one over R E Q. And a lot of times they put that answer down here. Fortunately, didn't we? Don't want one over R E Q. We want our e que hit the inverse button on your calculator flipped the Fraction 60/5. Let's get B 12 If I'm doing the math radio 12 homes 43. What is the current in the reading of the annular? So we won't know the current in this junction or in this branch right here? So let's I to it's a parallel circuits. So in order to find the current there, I two is V two over our two. We got no V two There parallel voltage vehicles, vehicles, vehicles Neither the visa equal everywhere. So if you know one place we know everywhere, we do know one place, you know the totals 12 really get 12 volts over 20 homes, which is going to be choice 2.6 amps. And then finally, what is the power of the 30 ohm resistor? Okay, Power. We confined through this series of equations here. We know the voltage and the resistance there. We could find I pretty easily, but might as well just stick with what we've got. We know the voltage in the resistance on the sea. P equals v squared over r. The V is the 12 member vehicles vehicles v so 12 squared. When were the resistance of 30 homes? You're gonna get choice 14.8 watts. The last page which graph best represents relationship between the magnitude of the electric field strength e around a point charge in the distance R from the point charge, let's get to electricity section Electric field is going because of forced over Q so there's no distance almost not affected. Nope, because forces que que que over r squared. You see that force drops exponentially as argues up. Which means E must drop exponentially, too, because F is dropping exponentially. So to get further away, evil drop exponentially like an inverse square, that downward curve and 46 several piece of copper wire, all having the same length but different diameters. Air kept at room temperature foot graph represents the distance are of the wires as a function across sexual areas. So several piece of copper wire all the same length but different diameters. This is the key thing here. Kept account would represents the resistance. Are the wires of the function across sexual areas. So R equals row L over A. You see here as a goes up, our goes down. You might think that means it's a linear relationship because there's no exponents here. Let's think about a A is the cross sectional area or the area of a circle? Well, the area of a circle is pi R squared, which means as the radius goes up or the diameter l say the diameter goes up, the area goes up exponentially, which means the risk resistance goes down exponentially. This one. We're also looking at an inverse square relationship who? We I'm glad you made it to the end of this video. Assuming that you did. I hope this help. This is the end of this particular version, part of this region's. There are other parts out there. I hope you check out. All right, That's it. Thank you.
5. June 2004 B2 Part 1: All right, This is the, uh, June 2004 physics regents exam. I am going to be going over just part B two in this exam. I do have videos for all the other parts encouraging to check them out. I'm not gonna put my answers in the answer booklet. Um, which may throw off some of these because they're graphs. I'll just try to pause and refer to that booklet when it comes up. Okay, so, uh, numbers 47 3 49 We've got a circular motion scenario here. We've got a car and driver combined, massive 600 kilograms, troubling and constant speed completing one lap of, ah radius of 1 60 meters and 36 seconds. First, we wanted to turn the speed of the car that we want to draw an arrow representing that force, and then we wanna determine the net force. So let's look the speed first. And to do that, I'm gonna draw little circle. This is what I'm going to use in place in the answer booklet for 48 as well. So here's my circle. I've got a car driving around that circular path. Um, I'm gonna just represent that car is a little box appeared, and somewhere over here is where it wasn't Answer booklet and the dead center was given. And we want to know the speed the car first. Let's just make a quick note list. We know the mass 600 kilograms. We've got the radius 160 meters and then we've got the time seconds and we're looking first and foremost the speed which is still just be rain as V, even though its speed and the reason I use the word speed instead of velocity is it's changing direction every second every moment. So its velocity is always changing. So we're looking at either the instantaneous velocity or the overall speed. Now, here's what I see. A lot of students to their realizes the circuit motion problem. They immediately jump to the circular motion question equations and most of them confined. These two FC equals that may see an A C equals. Have you screwed over? Write those down So they're gonna write. I see students do this on their answer work all the time. FC equals m A. C. In this a c is V screwed over and they say OK, cool Looking for V got our This must people I'm using and and they re arrange it for radical. They say vehicles radical a are. And either they just make something up for a or they incorrectly assigned with easing for a But you can't do this because we don't know this centripetal acceleration. This is not the way we go about solving for V. We will likely we use that in number 49 right? But for now, this is just not possible and stay. We got to go to the most classic equation for velocity, and that's straight up distance over time. And so I see a lot of kids get to this spot and then I still see a whole faction of them screw up the distance part because they say, Oh, okay, are must be distance. They write 1 60/36 that's not ready. There is the car travelling the radius of this path and 36 seconds. Is that what it's doing? Of course not. If you can actually try to envision and conceptualize what is happening in this problem, we have a card traveling around an entire circle in 36 seconds. So isn't it fair to recognize that the distance that it's traveling is the distance of that circle otherwise known as the circumference? Yeah, What we're looking at is really the circumference of the circle over the time. Now, in case you don't remember how to find the circumference of a circle, you do get this little cheat sheet here in the reference tables, your geometry and trigonometry and you probably see circumference. Okay, there it is. Two pi r. Go ahead and use that. It's there. I know it's not always preached about in class, at least not my class, but it's their circumference of the circle is two pi r Over time, that's what we're looking for. And this problem so finished that work down here, the glossy ends up being two pi times 1 60 meters over time, 36 seconds. I don't necessarily need to put the knowns in with the units because I already made a less . But it's always it's always good to be safe, and you're gonna get 27.9 meters per second, right? 48. Now we want to draw the net. Force the air orbs in the net force. And these were gimmes, thes air ones. That should be free points because you all should really do these. Every time you have a circular motion problem, you should know that always we have a center seeking net force. That's what centripetal means. Center seeking your net force is pointing towards the centre. Let me just do a follow up. Sometimes they ask you to determine the direction of the acceleration. Well, that's also center seeking. Where there is the force, there is the A because F equals M a c, they go to gather. I do see a lot of kids. Unfortunately, go ahead and draw this arrow either in as well or in place off because they always remember that there's some sort of hero here to you got to recognize this isn't a force. This is just the direction of the instantaneous speed. That is the direction and speed is pointed out that if it were to stop going in a circular path, if it were to stop turning inward, it would just drive straight. That centripetal force was gone. It would go forward. This is not right. And not only that, you shouldn't include it on a free body diagram you shouldn't including The answer is that it looks like you have two different answers. So I try not to include that velocity information. All right, now we're going to 49. We argued, use this equation here. We now know velocity. We already have the radius. ITT's just could be plugging and solve at this point. Ah, here is the tip. I want to give you on the meat. First plug ins, a 27.9 squared over the radius, 160 meters. Put that units in over here, too. And you're gonna get its in chipotle acceleration of Put it under that that 4.9 meters per second squared. Let's talk about free response. It's talking about these two point problems because this is important to know. Let's assume that you didn't know how to do 47. You couldn't figure out velocity, right? Were to lose your points up here. You're not gonna get either of them if you don't have a velocity of here. Right? This 29. 27 point. How are you to do this and shit like situation down here? Right. And that means OK, now you leave this plane, you lose. Leave this blank. You lose four of these possible five points. That's not a good start to the regions. Here's the thing. And I don't want you to do this necessarily. I'd rather you know how to do it perfectly. But let's assume you can't figure this out. Go ahead and put something in here. Vehicles D over tea. Whatever you do, come up with an answer. It could be completely wrong. Maybe you come up with an answer. It's like 69 68 67. I don't know, some crazy number. That's nine. And as I meant to do with this, you're to lose all the points here. But now, if you use that number down here for V yeah, that'll be wrong. Yeah, your answer will be wrong, but you'll still get full credit for 49 because of 49 is looking for is a whole different, isolated problem. You need to know that this is how you find acceleration. You've established that you need to know how to plug in and use your calculator appropriately. You've established that if you do it correctly with a previously incorrect number. You'll still get full credit. Don't leave anything blank. Toss something in or let's go one step farther. Let's say you didn't remember to do that. You left this completely blank or you didn't remember that number came in here. Now you get down here and you're all like all right, V squared over R. Oh, my gosh. I don't know, V. I know this is how I do what? I don't know. V and I see someone new. Kids on the regions have something like this down, and they just red question mark in the move. Right on. You're not gonna get any points, because in the region's exam, we award two points for these problems. You get one point for having the right equation the right substitution with units. That's the first point. The second point you get for the correct answer with units. So you've only earned part of that first point by putting the equation down. If you do not sub in with the units, you won't get that point. So let's do this. You don't know V Just make something up. Show us that you understand that an acceleration is something something meters per second squared. Put some random number in here. Maybe it's 12 meters per second squared over the 160 meters. Get some ran. You know what? I wanted to make this nice and easy math. Um, on. I guess I won't make it nice and easy map, because I can't take the route of 16 in my head very easily, cause I don't know why eso either. Which way? 12 over this. Whatever this number comes out some number. Okay, Some number. Yeah, you're gonna get it. You're to get a point here because what's gonna happen is you're gonna lose the point up top. You're gonna get the equation. But you're not gonna get the point for the substitution, because that's not a correct substitution V's wrong. So you're not gonna get that for its point. But then down here, some number with proper units will get you the point because that answer is correct. Based on your improper substitution. This is okay to do. You're not clearly establishing knowledge of physics, but you're establishing an understanding of this problem. You know that you're looking for some chips exploration. You have acknowledged that you don't know your velocity, but At least you struggle. You figured out a way to get that point to show the greater that you understand something, please scrape away. Try to get as many points as you can. OK? All right, I'm gonna stop ranting about how to get points. That's it for the rest of the regent's. Let's just get get get going here 53 51 or dealing with this information. Here we have an eight kilogram ball fired horizontally from a cannon. All right, let's right medicine that we have an eight kilogram ball, someone said. A mass of the ball was eight kilograms fired horizontally from a 1000 kilogram cannon, I said a mass of the Canada's M C. Initially at rest. The cannon is initially arrested, not overlook these hidden variables, So v. C zero, after having been fired The Mo Mentum. Make sure you reading these words correctly of the ball is 2400 kilogram meters per second east. So now the Mo Mentum is 2400 kilogram meters per second. It's e Some country east is positive. I see students not make knowns list all the time, and then eventually, when they go to plug in, they magically create that treat. This is either mass or velocity. It is not. It is the moment um 50. Calculate the magnitude of the cannons velocity after the ball is fired. I think about this. If in the beginning the cannon and the ball have no mo mentum then after the ball gets fired, the ball has some level of momentum. Remember in the beginning, the momentum was zero both afterwards the ball games 24 kilograms per second. Momentum Ford, Isn't it fair to assume that the cannon must also have 2400 kilogram meters per second of momentum backwards? They have to be equal and opposite. They have to be in order for the net mo mentum to stay zero This vector has to cancel out this vector. Therefore, non on Lee is the momentum of the ball 2400 kilogram meter per second, The mo mentum of the cannon isas. Well, really important because now, for number 50 all you gotta do is say well, pc will equal m CVC And since it's after the ball is fired, I'm gonna call his VC prime. The velocity after the ball is fired. So V. C prime is simply the momentum of the cannon divided by the mass of the cannon or the 2400 divided by the 1000 here to get a velocity of 2.4 meters per second. I'm not using answer booklets. I'm sorry I'm squeezing in here. You'll have plenty of space and using the actually answer booklet. All right. 51 we want in the direction of cannons. Velocity the cannon. Make sure you're reading these. Rate the canons of Aussie after the balls fired. If the ball is gonna go east afterwards in the overall momentum and beginning of zero, then the cannon must be going with dust. All right, let's move on. 52. They only resolve this wet land. Were women do and right. 52 during a five second interval and objects velocity changes from 25 meters per second east to 15 meters per second east. Determine the magnitude and direction of the objects Acceleration. Let's read during the five second interval and objects. Velocity changes from 25 meters per second east to 15 meters per second. East Baltimore. Positive that both east determine the acceleration. Oh, magnitude and direction both unnecessary. Alice should be nice and easy, right? A is changing velocity over time. My change is always final. Minus initial. So negative. 10 meters per second over five seconds. We should be getting a negative two meters per second squared acceleration. Now, in the answer booklet, you had this in his said meters per second squared and then had another line here for the direction. Well, you need to write is one or the other of the falling, but not a mixture. You can either right. Two meters per second squared west. Am I doing put the M s per square here? It's already there. Stutes again. You can either right to hear west or negative too East. However, negative to west is not appropriate because you gotta understand that this to being west is already against the original motion of the car hands. It's slowing it down or negative to east basically means while the negative basically is the opposite of east. So it really means to West however negative to west actually means to east. There is a difference. Make sure you understand that vectors. All right, let me continue. And I'm sorry. I'm taking salon go over this. I just think it's really important to point out these errors. I think sometimes the errors or the extra stuff is almost more important than knowing the solution. It means this video's gonna end up being longer than I anticipated. But you know what's worth it. You're doing this for review. I encourage you toe keep an open mind on those little inside stuff that you get told that aren't necessarily just the answer. Right. Okay. Let me go low. Quicker than which way started Conducting experiments determine the resistance of a label, but she applied various potential differences to the bulbs, recorded the voltages and corresponding currents. Ah, and constructed the graph below. So we have current versus potential difference volts, and we have a changing slope. Student concluded the resistance from the blood bowl was not constant. What evidence from the graph supports the conclusion? Well, you gotta understand that this graph Well, if V equals I r, we get our by itself. R is V over I, which means that either the over I or the inverse one over are being I over V either which way that means resistance will be represented by the slope. So technically, the slope of this graph is the inverse of the resistance. But you get the idea, I hope maybe not. I think you do. Therefore, this is a fancy way of saying How come those slope is chair? How can you tell if the slope is changing and ultimately all we need you to say is the slope is changing or the slope is not staying constant or the line is curving. Any of that is true. If you go and say all the current and the voltage changing causes the resistance that that's not really showing us the evidence. That's just restating what they already concluded. You have to say what they're concluding, why their evidence is true. 54 According to graph the potential difference. Increase the resistance. The label did what as the potential of the difference increased the resistance. Did what? Now let's think about it as we increase my voltage, my current or my increase in current decreased. Actually, let me state that a little different exit kinds of that backwards as my voltage increased. Yes, my amount of current didn't increase as much as they did before, but it's still going higher and higher it you're not seeing it drop down. Therefore, as my voltage increased, my current still increased. But did my current increase as much as it did earlier on? No. Hence, as I increased voltage, I ended up getting mawr more resistance because less and less current came through. Therefore, the resistance increases. While performing the experiment, the student notice that the bull began to glow and became brighter as she increased the voltage of the factors affecting resistance. Which factor caused the greatest change in the resistance of the bulb during her experiment ? Here's another unfortunate part is really the first half of the city paragraph really isn't necessary. Yeah, of course. As they increased voltage, the bull began to glow. Miss, cause a lot of students to answer all the current increased. That's not what we're looking at all here. We just want to know why would resistance changes that somewhat? What would cause the resistance of something that change? Really? The best way of looking at that is R equals row L over a. Is the l changing It was the aid changing? No. So therefore it has to be that thing called resistive ity or the ability of the material to provide resistance. There's a little concept. Well, you just gotta know. As temperature goes up, the resistive it even object goes up. Therefore it's resistance goes up. That's what we're looking forward temperature, temperature, heat and the any other thing that similar to that would have worked. All right, let's move on.
6. June 2004 B2 Part 2: Okay, 56 57. We have a student plucking a string and, um, the vibrations produce a sound wave with a frequency of 650 hertz. The sound wave produced can best be described is what What kind of wave This is. Ah, just a great way of saying What is a sound wave? All sound waves are always could be considered waves that are mechanical waves but specifically there laundry, tuna waves there, compression waves, they go back and forth. They go along the axis of energy motion not up and down. Like the trans words the first waves Dio. So it's definitely longitudinal. No, that all waves once they have been produced all waves. Once they've been produced, not just mechanical ways any wave. Once it's been created, its frequency will always remain constant choice to calculate the wavelength. The sound wave in air at STP So now let's look appear. We have a frequency we're looking for sort of my wavelength. If I look at my equations for my wave section, I see wave length and frequency or together here it means I need to know by velocity is well, I don't really see it anywhere else. I'm not dealing with refraction. This is an optics. It's gotta be this 1st 1 So I should now think. Okay, I probably know the speed. The speed of what? Let's read it again. The speed of a sound wave. Okay, let's look in the front page. Probably. It's usually where all that stuff is. Do we see anything out yet? Here we go. The speed of sound. 3.31 times 10 of the two meters per second or 331 meters per second. So no velocity. I just looked at the equation. Vehicles, wavelength, times frequency. There for my wavelength is my V divided by my frequency or 331 divided by 650. And we're gonna get 0.51 meters. Two pointer equation knowns with units. Answer with units. Okay. 58 beam of light travels through media max with speed of 1.8 times 10 to the eight meters per second. We want to know the index of refraction. Once I get my equations here, we're in the way of section somewhere in here. Ah, here we go. And is the knicks of refraction. See over V we Novy? What? See? Speed of light in a vacuum. We're definitely dealing with late from Page. I know what three by 83 by a three pointer by 10. 88. So see, we have meters per second an equal. See over V Just gonna divide you. Get 1.67 Okay, now last one for part B to last one for this video 59 project a housing initial horizontal velocity of 15 meters per second. I'm gonna call that V X horizontal in an initial vertical velocity V i y of 25 meters per second. We want to determine the projectiles. Horizontal displacement. That's D X. If the total time is five seconds now I teach an X y table. I'm going to write that down. Not all teachers do, but I do think it's helpful. The reason being my access, my wise, they cannot go together. They do not affect each other's motion. So you to put your definitive exes and the X and definitive wise and the White column. We know a equals G which equals 9.81 meters per second squared. Now think about this This sucker's going up in the beginning. This is definitely against. That's got to be negative. Got to include that. Time is scaler So that all scaler terms going both combs. Are we looking for now? I don't even know what I'm looking for. Horizontal displacement already wrote that and d x in the X dimension. The other thing that always realizes a is always zero. There is no acceleration. The X There are no forces acting on it. All right. For this one, it's just a simple as average velocity equals change in distance. Over time, eso my change in distance is going to be my average velocity times time. Nothing to catch here was to use Onley in my ex velocity. So it's 15 times five. That's it. 75 meters. Okay, that completes it for this worksheet. I hope this helps. I, um, will have the other parts up there. I hope you check them out. I think that they will be very helpful. All right. Thank you.
7. June 2004 Part C: All right, This is the Juno four Physics Regents exam. I'm looking at parts. See? Only in this exam our videos for the other parts. Check them out. I hope you hope you do. And we're leading off the number 60 through 62. We've got data here, and the you could eventually graph this data. And I just took this from the answer. Brooklyn pasted it right here. It's not, really weren't only belonged. So if you happen to be printing this test or looking at the printed version, this isn't really here, Mrs. Just the graph that I'm gonna use to correspond with 63 62. So 60 says on the grid provided plot. The data points for the force versus elongation. So let's do that first. We've got a It's always important. Read this stuff. So, in an experiment, student applied various forces to a spring and measured the springs corresponding elongation table below shows the data. So basically, there is a spring. We pull us with a certain force and it stretches a certain amount, and we keep increasing the force and measuring this elongation. So, perhaps, is a weight that we're putting on at whatever. We're letting it get into equilibrium. So we're gonna go ahead and plot. So we have a zero by zero. So it's important to actually plot this Europa zero. It does mean that the data started it with nothing. No elongation when there was no force. Then we're gonna go through and plot the rest. I'm gonna posits, Why do that? So I don't waste too much time, All right, I got the points plotted more or less. And I also grab myself a straight edge because I know when you need it, because 61 says drops off the best fit line. Now, I just want to point out my dots. You can tell already that it's not following an exact, perfect ideal scenario, which is good. Most experiments are not going to follow that. So we're doing our best fit line. Understand that you are not gonna be connecting the dots. It's the worst thing in the world to do. Don't be drawing a bunch of segmented spots here. This is not OK. No, that's gonna lose your points. It's probably to frustrate whatever teachers grating it, because I'm sure they have told you to not do that and the best. In my opinion, way to think about how to do a best fit line is that line that you draw needs to encompass the majority of points. Like I will say, I'll basically say the number of points on one side of the line should be equal to the number of points in the other. Settle in now I've got my ruler here. You would normally take your pen and draw a straight edge that that's not a real straight edge because it's just a part of my program going to go ahead and grab the straight line tool instead and play with that until it looks like it's raped and it doesn't need to start an end of the original two points. It happens to appear to be doing that right now. It probably should started zero because, you know, 00 is definitely a true point, but it doesn't need to finish in that last one. This looks like a pretty legit best fit line. Not everyone's gonna have the exact same best fit line, and I have, but you're going to get close and you get a plus or minus acceptable range. How 62 says using your graph, calculate the spring constant of the sprink. The key term here is using your graph. You'll absolutely have to use your graph. You can't just grab data points over here. You've got to use a graph anytime you have a graph, your first job should be to determine what is the slope of the graph representing here. We've got a force versus elongation. You may realize or recall, that slope over here on the left is equal to change. And why, Over your change in X your rise of your run this case is give me your four. So you're changing your force over elongation, which is also represented his action x So looking at what the heck is f over X equal to what we're dealing with spring. So it's probably gonna come into play. Let's go to the spring section of a reference tables here, which is in the back page towards the bottom. And here we have the two equations. So we have f equals K X one, right, the original equation down. Just we can see what we're doing here. Half equals K X. Well, you see here I don't have to divide my X over to get in the same format up here. So really, this, Um what we're looking for is this spring constant, which is the slope. So here was this cabin this spring constants a fancy way of saying determine the slope of your graph. So you've got to use data points off of your graph offer the best fit line that you drew. So let's look at a graph, and I'm gonna take two points that are nice. Clean inter sector. Since we started 00 that's could be my first point. I'm gonna take you don't need to circle it like I am this point a nice clean in our sector is going with the four by one spot to So I take that point. So I'm gonna say, here that k is my change in wire My change in half, which will be four minus zero. So four new ones minus zero four minus your final mice initial and then all over one minus zero, one meter minus zero. So we're gonna get four newtons per meter. That is the answer for number six that, you know, because your best fit line won't be the same for everyone, and not every will take the exact same points. Either You're gonna have a plus or minus acceptable range for these two. This set of problems. All right, let's move on 63 to 64 with a physics class that to design an experiment to determine acceleration with student on an incline on m. Sorry. On in line skates, coasting down the gentle incline. The incline has a constant slope. The students have tape measures, traffic cones and stopwatches. So I'm gonna put my incline over here just so I can show you what's going on here. We wanted for 60 Slava 63 describing procedure to obtain the measurements necessary and then for 64 indicate which equation should be used. Uh, these experimental one's got to be careful with them. Sometimes they're great. Gimme points. And sometimes there not give me points. Ultimately, you can't just say measure the velocity or measure the acceleration because you're not telling me how what you can say is measured the distance traveled by using a tape. Mention things of that. So here we go. I'm just get set up. One possible experiment. I'm going to say set up cones to mark the start in finish line. Have someone standing after the side with a stopwatch to time it. Have the students start from rest of the first cone. It's important to say, starting from rest, because now we can treat V I. Zero have the person to stop. Watch start time once the student begins to move as they travel down the incline, stop time when they hit the next cone, make sure that's didn't measures the distance between the two cones. We know distance, and from that you will have a set of variables that will allow you to determine the acceleration of the student. Now you don't need to get too wordy, but be careful. You don't want to say stuff that you aren't explained again. Like I said, don't say measure the final velocity because it's not like you have some sort of device that just measures the final velocity. Indicate what you're measuring. Indicate how the procedures going. But don't get too worried, because if you say something too much and you're wrong, you're gonna lose points. What equation should use? Well, if we look at it, we're gonna have initial velocity zero, you're gonna have changing distances. Some known value. You could have thymus, some known value. These three will all be knowns. So maybe right known known. We're looking for acceleration from this. It should be clear that we're gonna be looking at The changing distance is equal to V I t plus 1/2 a t squared. You don't even need to actually indicate. Ah, that you need that. You know V I t zero re arrange for a You don't even this show the final product. You just need to take a what equation needs to be used. That's it. Move along a rate. I'm coming back up top right corner here on me. Delete my graph. I don't need this anymore. We'll move my ruler off the side in case I do need that way to Ron. 65 to 68. Driver of a car made an emergency stop on a straight horizontal road. The wheels locked in the car skidded to a stop. The marks made by the rubber tires and the dry asphalt are 16 meters long. Thedc ours master 1200 kilograms and we want to determine a bunch of stuff versus the weight of the car. Well, uh, the weight of the car should not be tough. Difficult for you. You don't even have space science booklet to show your work here. I'm just gonna do it. Anyhow. Wait is mass times gravity 1200 kilograms. Times 9.8 in 48 1 meters per second squared. And you're gonna get 11,772 new ones. 66 captured the magnitude of the frictional force, the road applied to the car and stopping it. We do need to show work here. And the answer booklet. There'd be plenty of space, so I'm gonna make a brief list of knowns that I have here. I know the weight is 11,772. Neumann's I know. You see the marks by the rubber tires and the dress dry asphalt there 16 years long. That's the distance in which the friction was being applied. We know the mass of the car. I'm not sure how much that's gonna come into play. We know that it's a horizontal road. Whenever we have a car or any object on the horizontal road, the way is being offset by this upward force the support from the surface, which is the normal force. So not only do we know the weight, but we also know the normal force to have to equal each other. We know, Let's see, we have rubber tires on dry asphalt. That should be an indicator that we could be looking at mu. If you don't know that you're looking at me, you, if you write down the force of friction, is my unknown. You might realize that because when you look at the FF equation, it's equal. M u f n. And hopefully that triggers a look up on you and me was found all the on the front page in the bottom right box. Here, approximate coefficients of friction we're looking for dry concrete are rubber on drag concrete. And now the question is, Are we using kinetic or are we using static using kinetic or are we using static? So let's go back and read the problem. All right, so the wheels locked in the car skidded to a stop. That means the tires no longer rotating. It's literally sly eating across the ground. So the one what we're gonna be using is the kinetic mule. You might recall that Connecticut Mu is 0.68 So we do know that 0.6 amy was coefficient. So it's unit lists. All right? Now all we gotta do is indicate the original equation f f equals M u f n substitute inappropriately 0.68 times 11,000 772 because I made a knowns list that do not need to put units, and it's totally appropriate to do it. But we don't need to get rid of this stuff, right? And we're gonna get an answer of 8000 and 40 new ones. No, I don't think that's right. I think that was the rounded answer. Let me go ahead and type this in my calculator. See if a more accurate version, which I can give you 0.68 times 11 77 to 8005. Nunes, this was using, um, 12,000 for the rounded. Wait, I'm not gonna do that right. That's 66. My work is shown here and get two points for showing all the steps. 67 calculate the work done by the frictional forces stopping the car. Ah, you will find that work is equal to force times distance. We're going to use the frictional force, so it could be 8000 and five. What? We just got times that distance of 16 meters because it's a new problem. You got to put your units and make sure you don't gamble a little bit with that. And I'm gonna get an answer of one. We're going to multiply that times 16 128,000 and 79 Jules and 68. Assuming the energy is conserved, calculate the speed of the car before the Blake brakes were applied. So this is saying that all of the original energy disappeared. It went from nothing went to nothing. If you recall that work is force times distance. But work is also more appropriately changing energy. In this example, we need to understand that this is a change in kinetic energy. We start off going kinetic. We were moving in this speed hit the brakes slowed down, Stopped. We're looking for the full initial velocity because the final velocity zero. So, really, since the final kinetic Angie zero, we know that the original kinetic must be equal 228,079 jewels, which is going to be equal to 1/2 of M V squared. We know mass that was given earlier on way up top, 1200 kilograms, times V squared. So we gotta rearrange for V. Um, not gonna go and do the steps right now. I'm just gonna get to the point, get to the answer, and I'm gonna get an answer of 14.5 meters per 2nd 14.6 or so, depending on how early rounded cool it's going. Next page, uh, number 69 70 are dealing with this intensity frequency. Late graph suddenly is composed of various intensities of all frequencies of visible. The graph represents the relationship between late intensity and frequency based on the graph, which color visibly has the lowest intensity. Well, first easy way. Look at the graph, right? And so where do we have the lowest in 10 city? The lowest intensities right here, they said. There's no colors here. How did I know? Well, if we realize that that's the highest frequency of visible light that can exist, that's what we're saying. This is the highest seats to the the highest frequency of visible. Now you should recall the Roy G. Biv acronym. Some folks drop the I part Roy G biv e. Whatever. Um, this is an in order of increasing frequency. So as we go to the right frequency increases so right there alone. If you knew that, you know violence. The answer here, violet. But let's say you didn't know that. Let's get a reference tables. Let's look at the electromagnetic spectrum. Let's take a look at her visible light. Hopefully, you can see here that violet light has the higher frequency than red light. Right has been suggests that fire trucks be painted yellow green instead of red. Using information from the graph, explain the advantage of using a yellow green paint well again. If you remember the order of Raja Bev, we're looking at something like this. You see here that yellow green corresponds to the area of higher intensity well, intensities, brightness, therefore yellow and green, just by default, alone, arm or intense or more visible to be seen. So the answer that we're looking for number 70 years, they have higher intensity. All right, let's look over the right calm. Last set here, 71 to 73 Alfa Line of the Bomber Siris of hydrogen spectrum consists of light having a wavelength of 6.56 times 10 the negative seven meters. We want to calculate the frequency of this late so it's write down what we know. We know the wave length is 6.56 times 10 and the negative seven meters. We're looking for frequency. You might say I don't know what to do here, and you probably should, because we're dealing with light that should trigger something. But let's just go ahead and look at the equations anyhow, just to see what else we might need. We're gonna go to the, uh, modern physics section, which is halfway through this page right down here. And we know that we're looking for the frequency of the late right. So in order to find the frequency with might need to know the energy, so that's not could be enough. So must be separate area were Look, let's look upto waves. All right, so if we're in the way of section, you might see here that vehicles f lambda, so we confined frequency. If we also know V, which is the speed the speed of the light speed of light weaken in court. We can interchange V and C together. So really, we do know something else we know. See the speed of light in a vacuum We confined on the front page If you don't remember it 3.0 times 10 88 meters per second. Right now, at this point, we're gonna use that equation we just had instead of me running V equals Lambda African rate C equals Lambda effort F lambda. And so f equals C divided by Lambda, which is three by 10 in the eight. Divided by 6.56 by 10 in the negative seven. And we're going to get a frequency of 4.57 times 10 to the 14 hurts. That's the answer to 71 72. Wants us to determine the energy and jewels of the photons. Well, now that we have Lambda and Frequency, we can actually pick one of two different equations. Let's go back to the modern physics section. So when I just point out to you e equals e of a photo when we are dealing with photons here . Okay, So the energy is equal to H F or H C over Lambda. They're both appropriate. I often encourage students to use the one that has the known in it. Not the one that you calculated, in case you calculate this room. So I'm gonna do that. I'm gonna say equals H C over wavelength. So I do my work to 72 down here now, I can fit it in here. It's not a show. Your all work, so I'm not gonna agency over wavelength H and C are both in the front page. Your tables. See, we already wrote down. So I suppose we have that and we're gonna get 3.3 times 10 to the negative 19. And since it's a standard equation, it's gonna be in standard units, which is Jules and then 73. Determine the energy in electron volts. Let's go. The front page we see here that electron volts, where are they? One electron volt is 1.6 times 10 the negative 19 jewels. So if I have this many Jewel's I clearly have more than one electron volt. You gotta divide the numbers out. So your energy and e v well equal 3.3 times. 10 to the negative. 19 divided by 1.6 times. 10 in the negative 19. And you're gonna get right around one point 8/9 E V. All right, that's it. That completes the problem that completes this entire part. I hope this helps. Thank you.