3U2 - PP7 (Newton's 3rd Law).pdf - SPH3U UNIVERSITY PHYSICS FORCES L Newton\u2019s Third Law of Motion(P.137-141 Newton\u2019s Third Law of Motion Newton\u2019s

3U2 - PP7 (Newton's 3rd Law).pdf - SPH3U UNIVERSITY PHYSICS...

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12/4/2012 1 SPH3U UNIVERSITY PHYSICS FORCES L Newton’s Third Law of Motion (P.137-141) Newton’s Third Law of Motion Newton’s first law of motion is descriptive and his second law is mathematical. In both cases, we consider the forces acting on only one object. However, when your hand pushes on a desk in one direction, you feel a force of the desk pushing back on your hand in the opposite direction. This brings us to the third law, which considers forces acting in pairs on two objects. December 4, 2012 3U2 - Newton's Third Law of Motion 1 Newton’s Third Law of Motion To illustrate Newton’s third law of motion, imagine a ball shot horizontally out of the tube of a toy cart on wheels. When the ball is pushed into the cart, a spring becomes compressed. Then, when the spring is released, the spring (and thus the cart) pushes forward on the ball. We call this force the actionforce . F action (cart on ball) December 4, 2012 3U2 - Newton's Third Law of Motion 2
12/4/2012 2 Newton’s Third Law of Motion At the same instant, the ball pushes backward on the spring (and thus the cart). We call this the reaction force of the ball on the cart. The action and reaction forces are equal in size but opposite in direction, and act on different objects. F reaction F action (ball on cart) (cart on ball) December 4, 2012 3U2 - Newton's Third Law of Motion 3 Newton’s Third Law of Motion Newton’s thirdlawofmotion deals with these action and reaction forces. For this reason, it is sometimes called the action-reaction law. F reaction F action (ball on cart) (cart on ball) December 4, 2012 3U2 - Newton's Third Law of Motion 4 Newton’s Third Law of Motion NEWTON’STHIRDLAWOFMOTION xrhombus for every action force, there is a reaction force equal in magnitude but opposite in direction xrhombus the action and reaction forces act on different objects NOTE! Since the action and reaction forces are acting on different objects, they will appear on separate FBDs. December 4, 2012 3U2 - Newton's Third Law of Motion 5 reaction action F - F r r =
12/4/2012 3 Newton’s Third Law of Motion PRACTICE

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