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Totoro wrote on 2012-09-08 08:14
Hello, my name is Totoro and I have a question regarding Newton's Third Law of Motion, which states that for every action or force on an object, there will be a reaction force, which is equal in magnitude but opposite in direction.
My question is, how do things even manage to move while this happens? o_o For example, if you're moving a car, the car should be pushing at you with an equal force right? @___@
My teacher gave me an example of how your weight pulls you down toward the earth, but you are also exerting the same amount of force upward, so you just simply stand on the earth, not breaking through the floor going to the center of the earth or anything. But if that happens, how come you're not flying upward or anything? @________@
Sorry if my questions don't make sense :( I am slow and I am only 3 weeks into my AP physics lulzzzzzzzz
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Enhalo wrote on 2012-09-08 08:43
So it's the same magnitude of force but on different objects, no?
Eg.
If I push my book across the table, the book pushes against me as well by the Third Law. So let's call my force F1 and the book's force F2. So... Mathematically, F1 = F2. However~
F = ma where m is mass and a is acceleration. Since my mass is much more than the book's mass, I'll experience a much smaller acceleration as opposed to the book that will experience a much larger acceleration.
Hope this helps~
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Burningsky wrote on 2012-09-08 10:20
Like enhalo said, F1 = F2, called equilibrium (things don't move). If two people push you in opposite directions with the same force, you feel squished but don't move either way.
As for your question, yes the car is pushing you back with equal force, but that force is put against the force of friction (learn about it later) and you don't go sliding off in the opposite direction when you try to push the car (though if you did it on ice, or some other frictionless surface, you might.)
You can transfer force to move anything, but third law says you go flying back just as hard.
The equal and opposite thing doesn't always apply to one object, it just means all the forces have to add up to whatever it was originally. (i.e. things that start at rest have to equal zero)
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Totoro wrote on 2012-09-08 18:26
Thaaaanks, I think I understand now :thumb:
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NomadTrooper wrote on 2012-09-11 13:53
Boring answers. This vid's more fun and sorta related.
[video=youtube;jHbyQ_AQP8c]http://www.youtube.com/watch?v=jHbyQ_AQP8c&feature=g-hist[/video]
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Enhalo wrote on 2012-09-13 06:48
Quote from NomadTrooper;949816:
Boring answers. This vid's more fun and sorta related.
[video=youtube;jHbyQ_AQP8c]http://www.youtube.com/watch?v=jHbyQ_AQP8c&feature=g-hist[/video]
Nope. Didn't propagate the error.
Also, we answered it quicker.