Physics - 2D Kinematics - Horizontal Projectile Motion | Corey Mousseau | Skillshare

Physics - 2D Kinematics - Horizontal Projectile Motion

Corey Mousseau

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3 Lessons (27m)
    • 1. PhysicsCourseOnline

      0:16
    • 2. 2d Kinematics 4 Introduction To Projectile Motion High School And Ap Physics 5

      13:31
    • 3. 2d Kinematics 5 Horizontal Projectile Motion High School And Ap Physics 6

      13:05

About This Class

Physics is all about the world around us.  We live and experience physics every moment of our lives.  For most, we take physics for granted and never really truly understand how this amazing world works.  

This course is the next in a series of courses covering the physics topics of One and Two Dimensional Kinematics. 

It's time to start launching, throwing, and shooting thing with projectile motion!  This course eases you into two dimensional motion with a focus on horizontal projectile motion. I break down projectile motion into each of its dimensions and walk you through how to solve some fun projectile motion problems!

You should complete my prior courses in this series before completing this course.  

The complete order in which my courses covering 1D and 2D Kinematics are as follows:

To be honest, I fundamentally believe every single human should have a basic understanding of physics.  This is especially true for anyone working or aspiring to work in any field even remotely connected to the STEM world.  This includes obvious professions such as scientists, engineers, and doctors, though also include many surprise fields such as law enforcement, athletic anything, computer science (and all related fields), law, animation, and much more.  

I am a high school physics teacher by day.  I create the majority of my videos for my own students.  My courses all follow NY State high school physics entirely, as well as the nationally renown AP Physics 1 & 2 curriculum.  AP physics is exactly the same thing as any algebra based college intro physics course.  

If there is enough interest I intend to share out all of my courses which cover all of the remaining topics associated with AP/College physics.

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. 2d Kinematics 4 Introduction To Projectile Motion High School And Ap Physics 5: Hey, guys. So here we'll talk about projectile motion. What the heck is projectile motion, right? Well, you know, projectile motion is a fancy way of saying free fall, but in two dimensions. Okay, so it's two dimensional freefall. Remember, the definition for free fall is an object solely under the influence of gravity. So we remove all other accelerations or forces, which and now we haven't learned in Do you tell yet? But you probably the idea eso projectile motion is an object travelling in two dimensions. But the Onley force acting on it is still gravity. So instead of it being a ball that we drop and see how far it falls. It's an object that's good travel both forward and up and down. Okay, sketch a better path of that. So that's the definition in reality, Of course, in real life, we do have a resistance, so we will have to consider that. But when we're setting up our physics in this class, we are going to ignore the effects of air resistance. At least in terms of quantifying it, we will understand its effect conceptually. Okay, so there are two core types of project I motion that we could be talking about. We've got more or less what's called horizontal project emotion, and that's an object that's initially released with only horizontal velocity. To see how that vector, which I'll represent his V is to the right horizontal projectile motion eyes still influenced by gravity, of course, but it starts off with no y velocity. It's on. Lee got X velocity, and it'll still travel in a projectile path like so and the others tight is angled project , um, which I guess is the best turn for it on angled project I motion is one in which the ball or the object has velocity in both dimension. Originally, both the vertical end, the horizontal. So it would be some velocity at some angle and angled project emotion And that, um, you know, goes up and then it comes back down or whatever, Like, in that sense. Now, you know, as is the case with aw physics problems, they could get a little bit more hair eating this. And so you know this this series of videos you just got to the basics. This video is get a focus on horizontal only. And then the next video we'll focus on angled. I'm gonna go through, work out some examples, talk about some concepts to do both, and you just wrap it up that way. Okay, so let's do this and you get rid of this guy and this focus on just this guy. Also another thing understand, is the path in which the projected child's, even with the angle, is always referred to as a parabolic path. And that makes sense. It looks like a problem, right? So, yeah, I don't know, You know, don't over think it's a parabolic path. That's it. Okay, so I don't know. Let's see. Let's talk about some constant first. So a projectile that's traveling under the influence of gravity and only them and influence of gravity. It's give me traveling in two dimensions. We're gonna have a horizontal mentioned. We're gonna have that vertical dimension. And remember when we talked about vectors, you always have to separate your dimensions. When you do your physics, you can't combine your ex, and why variables or your vertical? You're horizontal and verticals. You have to keep them apart. It's a painstakingly clear project emotion, because the acceleration due to gravity on Lee effects one dimension, you're not gonna have the acceleration due to gravity pulling it forward. You're gonna have it pulling it down. So the first concept is that the acceleration due to gravity on lee effects the why or the vertical dimension. Hence, you always have to make sure you separate your ex from your wife or your horizontal from your vertical however you want to think about. Okay. Second, you're horizontal. Component will never change. So if I know my horizontal component right from the start is two meters per second as an example that it's gonna stay two meters per second the whole way across while it's moving the Onley velocity, that'll truly effective that will be truly changing is the vertical, because acceleration to gravity is pulling it down or or slowing it down, it's still pulling down with slowing it down as it's traveling up and increasing speed as it travels back down. Now, of course, when we consider a resistance, it will affect both dimension, so that's could be a little different again. We don't to quantify that we just need to do that conceptually, and I'll draw that example you know, momento. Okay, Another thing I just want to know about before I get too far ahead into an example. Problems. It's really, really good to organize your values. Like I've said multiple times you have to separate. Your ex is from the West. You might as well make an X y table when you do that. Separations. We can. Uh, yes. We don't forget that. Right. Okay, um, let's talk about your resistance. And then I'm gonna give an example about two tandem objects. One falling in one, projecting. So here's my object. This is where it lands if I do not have a resistance. And my question to you is if I include a resistance. If I have Aaron, the way in this particle is still shot with the same initial velocity. How will it affect the way it lands? Now what we're looking for is for you to understand that that velocity vector, which is horizontal, will experience some resistance. So it will actually this example, including a resistance it will actually slow down, so won't land is far away. All we're looking for when you ask the style questions, I'll do this one purple, so you can see the difference. All we're looking for. We asked the style questions is free to conceptually understand that will still follow a parabolic path. But it'll just end closer, and that's because it's slowing down the horizontal sense. Do not do what I'm about to do. Do not do what I'm about to do. I see students try to get all funky with these things and get all weird. They're like, Oh, it goes up and it just does something like this. And no, we're not looking for anything like that. Okay, this isn't a paper airplane catching the wind. This is this Just a regular old projectile Don't go and say goes further away. Resistance means it impedes the motion, so it's not gonna make it further out. A resistance is gonna slow its effect down. It's not when boosting it, it's air getting in its way. Okay, that's it. Concept a resistance is over. So the other one I want to ask you is, and this is ah, classic example, and I'm gonna go ahead and use the bullet and shell scenario. Mythbusters actually did an episode on this. I encourage you to check out their bullet and shell episode. It's pretty gnarly. Uh, and the question is, let's say we have a gun. And remember, I fail Physical physics are so I'm not very good at taking the time to draw my stuff. But pretend this is my gun here, and it's gonna shoot a bullet out of it. That is a terrible gun. Oh, well And inside years a bullet and it's gonna fired out. Okay? And the question goes, let's say we're some distance above the ground when you fire a bullet for 10 and a pretty terrible line. So a little bit better pretend that this is a nice, perfect scenario Where the bullet, the gun, it's all perfectly horizontal. And this bullet will ejected the shell cartridge completely down. It won't shoot up on an angle away from you. It's just gonna drop the shell as the bullet shoots forward and the question goes, What will hit the ground first? What will hit the ground first? Will it be the bullet as it shoots through the air? Will that hit the ground first, or will it be the shell as it falls down? Which one hits the ground first? Think about it. Will it be the bullet or the show. So questions you might be asking. Well, what's their Maxwell? Let's debunk that. Remember, in freefall Mass has no effect. So it will be They will be falling a za result of the election due to gravity the same capacity their masses. No effect there. Now posit. If you're not ready to answer some about to give the answer, here is what I hear. A lot of students, a lot of folks. A lot of folks will say the bullet will hit the ground first. Like to say Well, because it's traveling super fast through the air, it's gonna cruise towards the ground faster UK The majority of people will say the other way around on their going to say that that bullet is going to hit the ground significantly . Later in the show, you said that shall hits the ground. That bullet is still cruising through the year because it's going so fast. So they're they're suggestion is that because it's going at such a high speed that it will take longer to hit the grounds. That's a logic example. Our logic, I thought. I mean, I know that people think it, but I'm telling you both of those are completely wrong. It is the third option. Kind of a trick question. They will indeed both hit the ground at the same time. I know it doesn't seem very obvious, and you've probably never actually shot and paid attention. This So you never shot a gun Attention with a bullet in the shop. It So I can change this scene example which I'm about to do, uh, with something rolling off a cliff or something falling from the same time. So keep this in mind, and I'm gonna show you why I'm gonna mathematically show you why in a minute. But, uh, they will hit at the same time. Why is that? Let's go through and give an example that you might have actually experienced in real life . Uh, let's say, Well, I don't know. You and a friend are off swimming when there's like a diving platform course, This is water down here on this common pool of water and you guys get all silly in. Your friend leaps off, not up at an angle, but it shoots out, you know, come back and they run out and they shoot out at an angle horizontally away from the edge and then you you just kind of felt like just doing kind of a pencil dive and you just dropped straight down. So you had no initial or is on a velocity or vertical velocity ball. And your friend has a starting horizontal velocity but no initial vertical philosophy. The question is, which one of you hit the water first were to know the answer. I just told you, uh, objects travelling at the same initial horizontal are vertical height undergoing the same initial vertical speeds will indeed hit the ground the same time. And I asked you earlier Well, why is that? What's the reason for this? Simply because of this gravity, G Onley affects that e versus a bit Oh, well Onley effects vertical motion or the Y values therefore well, So we are traveling horizontally. Gravity is not increasing or decreasing that horizontal speed. It's gonna pull you down. The same is oppose everything else down. Add to that ex motion so that horizontal motion has nothing to do with vertical motion. Where why motion they do knocks, interactive each other at all so that extra horizontal that speed has nothing to do with the ability to fall. And if it did, it would be pretty gnarly. That would basically be implying that as this person runs out, gravity basically slows down or even stops existed. Also there. Just like out here, I totally see them picture that they're out here running. We then they realize it in the air. Maybe. And I fall down, you know? You got that looney Tune effect now, that's not happening. And I'm gonna try to kind of draw it for you. I'm not gonna concrete put numbers in right now. What we've got going on here is this blue guy, Aziz, he's a little bit further on. He has phone a little bit, but that horizontal speed, it hasn't changed. This is V. This is Is there any V X will say? Is there any reason for that V X to have changed? No, But not only does he have some Vieques, but he also has some V wiring. And then this Ah, peak guy, which I clearly didn't draw this guy too far out. He's only fallen a little ways as well. Seeing distance, he's fallen. Oh, and he now also has some of you and he has the same view eyes this guy does, because they both fell from the same height with the same initial velocity. And if I were to draw out a sizable time later, this guy would be cruising down here. His view. I would increase by a lot because gravity still acting on him. And then this dude over here, he's gonna have that same downward speed. But he's now moved over a distance. So he's he's still out over here. He's still cruising off with the same the X. But now his view, Why is increased Just like this guy? And I got to keep doing this until they splash into the water. This guy's traveling in that parabolic path, and this one's just straight down. Excuse that you just blasted beat. That means that. All right, so maybe I should talk some numbers in here now again, G only effects the Y and X only affects the X Y only affects the why do not marry these two together or is on Project I motion. That's the same thing for vertical. By the way, vertical projectile motion the G only forget affects the like the X's and y's do not go together. Let's do this. I'm gonna end this video. Here's the basics and protect emotion. I'm gonna do another video dealing with just horizontal and another video of just angled the horizontal one. I'm gonna incorporate the breakdown of the vertical motion within its You can kind of see this example with numbers. Cool. Thank you. 3. 2d Kinematics 5 Horizontal Projectile Motion High School And Ap Physics 6: Yo, Luso Here. Here we go. Got to go through a horizontal project of motion. Problem Not gonna write a whole problem. Now. I'm just going to draw and say it out loud, and I will write some knowns as I do it. So I've got a object that's going to start off. Will say, Oh, I don't know, 11 meters above the ground. And it is going to leave that cliff with a initial speed or is on till speed on Lee of will say six meters per second. Okay, The question is, how far from the base of the cliff. That's what we call range. How far from the base of the cliff? Well, the projectile lands. Okay, so what's the range? Um so me draw in the path so we can all see it. So what is Delta D x? Also known as range, And this thats years height, great vertical, which is dealt, Do you? Why? So what is the range? Okay. And I'm gonna try to draw this projectiles of velocities as it goes. Not only that, not only gonna ask you what its range is, I want to know what is its final Uh what is its final vertical velocity? Or the velocity right before hitting the ground? So the two questions are a Is the range and B What is the y f? Of course, we always take great before hitting impact. And, well, if it's a personal, say it's water or big, cushy pillow or something. I don't know. I'll let you kind of play with that. So first things first. X y table. Stefan. The best route You don't like to organize? Sorry, but X y table will help a lot. And that means put all your variables that, you know, when the X here and you're unknowns and all the variables, you know, an unknown that or why only here. And if there's something that's in both dimensions, we do have to find those components. In this example, we only have, uh, individual dimensions, given nothing's at an angle. So we should be okay here. So let's go on with what we know here. What we know Vieques is six meters per second. So that goes in the X dimension. Now, remember, just for a recap, maybe I'll write them all down here. We've got time. We've got displacement. You've got initial velocity. You've got final velocity and you have exploration. These are the five motion variables, right? So my question is, what is Vieques is a V i rvf It's both. This is average velocity and it will not change. So we can say this is equal to I'm just gonna read it for the giggles of the I X and V F X . They're all equal to each other. Why is that? Because there is no acceleration in this dimension, so they're equal to each other. Cool. It makes it a little easier. Ah, we don't know D X, that's an unknown. And eso now might be struggling here because we think, How many variables do we need to know to find all of them? Three, We seen only know one. Well, I guess technically, too, there's something else we need to figure out. That's right. X a X or my acceleration is zero. I don't write this in a lot because it's implied it's X dimension. But if you're one that tends to forget those things, you ought to write this in. Okay, so now we're looking at my variables here. We still don't have enough. There's something else we need to know because every every equation either incorporates acceleration or incorporates time in it. So that's the other variable we need to know. We need to know the time the projectile was in the air Notice. I haven't given it to you yet. We're gonna come back to that. Let's get to my Y values. What do we know in the wider men? So we know we're falling 11 meters, right? And we're falling down 11 meters. I'd like to put down that my displacement is indeed negative. 11 uncles. I'm looking at it. I'm thinking myself, That must be must be the only thing we know. I can't make sense because in order to find anything, we need everything. L we need at least three things. There's gotta be more here. We know. Well, let's start off with the easy one. Why are we falling down, right? Yeah, our acceleration. That's the acceleration due to gravity. That's also gonna be negative. It's directing us downwards. So 9.81 meters per second squared. It's still not enough to find anything like on both dimensions. We still don't have enough information. There's gotta be something else we know when there is. Let's look at the very, very beginning and think about all our equate. Are variables left time to be no time, no about initial velocity. What's my initial vertical velocity? Do we know that here we do it. Zero In the beginning, we only have this X velocity. So that's what kind of a hidden project. Emotion variable with horizontal problems. Your initial y velocity is indeed zero. Look at that. We have three things That means we can find V two y. That's one of the things I'm looking for. I wrote the why after was the same thing and we probably confined time. Check this out. Any scaler term actually is equal in both dimensions. Any vector term is limited to the one dimensions and the d and air all vectors, so they have to stay in the X. But time, times scaler doesn't matter which way you're going. Time moves on definitively, no matter what. So the time in this column is equal to the time in this combat. The same thing. The time in which you fell down is the same as the time in which you moved forward. It's not like you separated your body. You hit the ground sooner than you went forward. That it's illogical doesn't make sense. These times have to equal each other. Now, remember earlier in the X column, we didn't have enough stuff to find things. We need three things. We only have two. Well, now look over here. We have three things in the White Column. We confined time. And then once we find time, it is the same time in the X column, So check it out. This is a decent role, thumb. It's not forever true. So don't just memorize this, but it does help. You're gonna typically be using the y dimension to find time. And then you're gonna use that time in the X dimension to find range. It's not always that way. You'll see some examples down the line Where you gonna find time from the X first, but more that more often than not gonna use the why to find time. That's what I'm gonna do. First I'm gonna find time. It takes the fall down vertically that I'm gonna use that at the time in the X dimension to figure out how far forward it went and then I'll come back to part B and go back to my wife to mention Okay, So to find time properly, we are going to go ahead and he's the y variables. So remember the rule, your exes and your wise cannot go together. Your exes and Wise cannot go together. So we have to make sure we only use my wife dies. If I'm looking over here to find time, I can Onley use these so we'll ignore this. We think about what equation used. So now what I want to do is think about what equation incorporates d a v i and t in it. You don't look it up or think about it, posit Ray. Now challenge yourself. Okay? Tell you which one is Delta D on a subscript, that is why is equal to V I and I'm gonna add the y in their times T plus 1/2 a t squared instead of me putting a I'm gonna put G that way. Don't mix it up. I could put a supply if I want to. Here's my equation. And this equations actually pretty easy to use right now because my wife velocity starts off zero. So I'll go ahead and do this in my black marker. That's gone. This whole thing is gone. I'm looking for time. I know. D I know. Jeez, I get this offer tea so that you were the 1/2 about the play Both sides by twos. And I say to delta, D Y I Then divide both sides by G and that's equal the time squared. So I need to give you the square I'm gonna take the square Writable sides Rock on T therefore equals the square root of two times negative 11 divided by negative nine point. Eat one. Now, I understand I'm not putting my units down here cause they already did up here. But if you want to be safe but your units in your negatives cancel out of my radical will be good. Was tossed this in my calculator and see what we can do. Two times. Negative. 11. Divide up by negative 9.81 And I'm gonna take the radical that hole inside term not going to get hung around that toe 1.5 seconds. Sweet. Now that I know that time that time goes in both dimensions I could get rid of my unknown. And you're a man known. I'm gonna say says 1.5 seconds and this is 1.5 seconds. Possum. I'm gonna finish this work right in. Here's your so I can leave this here for a little while, but I think I might have to erase, um, stuff. We'll see eso now. Remember, what I really care about is my arrange Now I have one too. I have three variables. I'm looking for de suite. I'm gonna go ahead and use the really easy equation. The very beginning. I'm gonna say the average velocity is equal to the change in distance over time. Not gonna subscript these with exes. Now, pause. I could have used Ah. Could have used. Well, I don't know. I guess I could have used the one that has the a n it, but a zero. You know, I could have used this one down here and let me write it down. I just thought I was kind of mumbling whether or not I wanted to confuse you or not, but I could have used this equation. Okay, I caution you not to do that cause he might unintentionally by default pug g in here and is is there an acceleration? The X axis? No. If you need this in your knowns list, you realize that zero d is v X t. Well, that's what this will end up being. When I rearrange this, it's the same equation. Delta D X equals V x times time, And that bar over the top just means on average, will it stays the same the whole time. So that's cool. Let's go in and plug in our values. And six times the 1.5 we just found right. And I could do that in my head. That's nine meters. Awesome. Nine meters forward. Gnarly stuff. Right there. Okay, last. But we've got to do I am all over the place of mine. Marker colors seal. Do the deep blue. Yeah, try to squeeze this in right here. What is my final live velocity? Yeah, I don't normally like doing that. So here it is, right here. I want to find my wife. Velocity. I've got 123 four y variables. I'm looking for the fifth. I can use whatever equation fits my fancy. I'm gonna say v two equals V one plus 18. Some say V two. Why? Because the one why Waas gt the 10 So let's just give you g times to your 9.81 times 1.5. And so right before impact we're cruising down with a speed of what's a 14.72 meters her second. And that's the downward speed. So if I want to get technical here and draw this down here right before hitting the ground down here, I've got a vertical speed of 14.72 meters per second. I've got a horizontal speed of six meters per second. That's enough for the high school curriculum. If you were in the AP or college level curriculum, you were likely gonna have to find this resulting velocity new just could use pi fag here, and then you're gonna use inverse tan to find the angle. All the stuff that I've done in the past vector video, um, challenge yourself. Try that on your own. I'm not gonna go ahead. Okay, that's it for horizontal project emotion. Next video is on vertical. Thank you