25_third_law

# 25_third_law - Lesson 25: Newton's Third Law...

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Lesson 25: Newton's Third Law (Action-Reaction) Newton came up with one more law when he started thinking about the interaction of objects. He had already talked about what happens when there is no force (1st Law). He then talked about what happens when there is a force (2nd Law). But what happens when you have objects interacting, affecting each other? The 3rd Law (The Law of Action - Reaction ) “For every action force there is an equal and opposite reaction force.” Anytime something applies a force, there will be an equal and opposite force back in the opposite direction. Push on the handle of a lawnmower to make it go forward, and it will push back against you in the opposite direction with just as much force. This is the pressure that you feel of the handle against your hand. There is one ultra important thing to remember when you are looking at action - reaction pairs. The two forces that you are looking at are each acting on different objects! If you are examining what you think are action- reaction forces, but the forces are both acting on the one object, it is not an action- reaction pair. In the above example, you exert a certain force on the lawnmower . The lawnmower exerts an equal force on you . Two objects, two forces. Some examples of action- reaction forces depend on the objects being in direct contact, meaning that the two objects involved are actually touching each other to exert forces on each other. These are called " contact forces ." 1. Action: the tires on a car push on the road… Reaction: the road pushes on the tires. 2. Action: while swimming, you push the water backwards. .. Reaction: the water pushes you forward. Action-reaction pairs can also happen without friction, or even with the objects not touching each other, known as " action at a distance " forces … 1. Action: a rocket pushes out exhaust… Reaction: the exhaust pushes the rocket forward. One of the original arguments that flight in the vacuum of space was impossible was that there

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## This note was uploaded on 12/02/2011 for the course PHYSICS 235 taught by Professor Staff during the Fall '08 term at Rutgers.

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25_third_law - Lesson 25: Newton's Third Law...

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