In this lesson, you learned about Newton’s three laws of motion and the ways in which they apply to the game of baseball. You also took your own notes on the meaning and application of the three laws. For the final assignment, you will use these notes and other evidence presented in this lesson to create a multimedia project, or write an essay, in which you describe and apply Newton’s three laws of motion.
Keep in mind that the three laws of motion are such a regular part of daily life that you might not notice how often they affect you. What do you think is happening as you’re picking up books, or sliding a chair up to a table, or typing on your keyboard to go through this lesson? There are endless possible scenarios to choose from.
If you create a multimedia project that requires a social-media, video or audio platform that is not directly offered by this lesson, you will need to post it to a file-sharing site (Dropbox, Google Drive, and Microsoft Teams are examples) and then upload the link to the Write It plug-in. Here are some ideas for what you might want to do:
Use Organize It to outline your ideas. You can review your notes in “My Work” as well as any of the following videos and glossary terms.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Manager:
The first part of Newton’s law of inertia is pretty straightforward. An object at rest will stay at rest, unless and until it comes in contact with an unbalanced force.
That means that this baseball isn’t going anywhere, unless it encounters another force. Say a wind gust knocks it over, or someone picks it up, like this.
So the ball stays at rest, until someone or something moves it, or hits it.
The second part of the law—an object in motion will stay in motion, until and unless it comes into contact with an unbalanced force—might take a bit more imagination.
There are many unbalanced forces in baseball: friction, gravity, air currents, to name a few. For this example we can use friction. A grassy infield has a great deal of friction, since grass growing out of dirt is rough and can be a little bumpy.
So if I hit a ground ball, the friction from the field is gonna stop the motion, pretty quickly.
Okay, let’s say we were playing this game on ice.
Ice is a smooth surface and slicker than grass and dirt, so it has a lot less friction, though it still has some.
Less friction, so the ball goes farther before it stops.
So what if I hit this ball, but in a place where there is no unbalanced force at all—no gravity, no air currents, and no friction?
With nothing there to stop it, the ball’s inertia continues, and the ball stays in motion, forever.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Manager: Newton’s first law asks: What happens when there is no force acting on an object? And the answer is, inertia.
Newton’s second law asks: What happens when thereis a net force acting on an object? And the answer is, acceleration. To be more exact, the law says that acceleration is equal to the net force someone puts on an object, divided by the mass of that object. So here’s an object. And here’s someone who can apply some force.
Even though this is a baseball, we’re going to put an “M," for mass, on it, because mass is a huge part of the second law. We’re going to call the net force the pitcher puts on the ball "F." And when the ball leaves the pitcher’s hand it moves with ”A” for acceleration.
I’m giving the pitcher the ball, which again is the mass.
He’s working up some force to put on that mass.
Nice pitch, dude. Alright, let’s get the bowling ball out here.
Pitcher: Huh?
Manager: So let’s say you put the same amount of force on the bowling ball. What’s going to happen?
Pitcher: Um, my arm is gonna fall off?
Manager: Hah, no. You’re going to put the same force on the bowling ball as you did on the baseball. So that’s going to affect the acceleration, right?
Pitcher: Mm, okay, whatever.
Manager: Let that ball rip, same as before. The bowling ball didn’t go as far. Its acceleration dropped, even though the same force was applied to it. Same force, but 50 times the mass; the acceleration drops, a lot. Let’s write it out.
That awesome acceleration you achieved with the baseball; you got that acceleration by throwing the baseball with your net force. If that’s a math equation, you’re actually dividing the net force you put on the ball by the mass of the ball itself.
Then, that not-so-awesome acceleration you achieved with the bowling ball?
You got that by applying the same net force you had put on the baseball onto the bowling ball, which has a mass that is 50 times greater than the mass of the baseball. So if you take the 50 out of this side, you find… yup, the acceleration from the bowling ball pitch is 1/50ththe acceleration of the baseball pitch. Much slower.
That’s Newton’s second law in action. Acceleration equals net force divided by mass.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Pitcher (to Shortstop): Hey, man. [The two chest bump]
Manager: You two just acted out Newton’s third law. My work here is done.
Pitcher: We did?
Manager: Yeah, you two exerted equal forces on each other even though one of you is bigger than the other. And then the two of you went in opposite directions. See what I mean? Maybe not. Okay, let’s play it out.
[Pitcher pitches, Manager slams a line drive]
Manager: So what happened there?
Pitcher: Um, you hit a pretty good fastball.
Manager: Actually, the bat hit the ball. And the ball hit the bat. They hit each other, with equal, opposite force. Take a look.
Manager: See, the ball is object one, and the bat is object two. Object one pushes here against object two, so the ball bends the bat… And object two pushes against object one, with equal force. So the bat bends the ball.
Pitcher: Actually, the bat crushed the ball.
Manager: Bend or crush, the point is that the force of the bat on the ball is the same, or equal to, the force of the ball on the bat.
Pitcher: The force the bat exerts on the ball, is equal to the force the ball exerts on the bat. And those forces cause the ball and the bat to go in opposite directions.
Manager: Now you get it.
Pitcher: Whenever one object exerts a force on a second object, the second object exerts a force of equal size, but in the opposite direction, on the first object.