s11 (c) Newton's 3rd Law (Action-REaction Law)
If you push on the ground with 50 N of action force, then the ground pushes back with exactly 50 N of reaction force. According to Newton's third law, for every action force there is an equal and opposite reaction force.
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Newton’s Third Law of Motion: Newton proposed that whenever one object exerts a force on a second object, the second object exerts a force back on the first object. The force exerted by the second object is equal in strength and opposite in direction to the first force. Think of one force as the “action” and the other force as the “reaction.” Newton’s third law of motion states that if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object. Another way to state Newton’s third law is that for every action there is an equal but opposite reaction.
Another way to state Newton’s third law is that for every action there is an equal but opposite reaction.
Another way to state Newton’s third law is that for every action there is an equal but opposite reaction.
Action-Reaction Pairs: You’re probably familiar with many examples of Newton’s third law. Pairs of action and reaction forces are all around you. When you jump, you push on the ground with your feet. This is an action force. The ground pushes back on your feet with an equal and opposite force. This is the reaction force. You move upward when you jump because the ground is pushing you! In a similar way, a kayaker moves forward by exerting an action force on the water with a paddle. The water pushes back on the paddle with an equal reaction force that propels the kayak forward.
Do Action-Reaction Forces Cancel? The action and reaction forces do not cancel out because they are acting on different objects. Earlier you learned that if two equal forces act in opposite directions on an object, the forces are balanced. Because the two forces add up to zero, they cancel each other out and produce no change in motion. Why then don’t the action and reaction forces in Newton’s third law of motion cancel out as well? After all, they are equal and opposite. The action and reaction forces do not cancel out because they are acting on different objects.
Do Action-Reaction Forces Cancel? The action and reaction forces do not cancel out because they are acting on different objects. Earlier you learned that if two equal forces act in opposite directions on an object, the forces are balanced. Because the two forces add up to zero, they cancel each other out and produce no change in motion. Why then don’t the action and reaction forces in Newton’s third law of motion cancel out as well? After all, they are equal and opposite. The action and reaction forces do not cancel out because they are acting on different objects.
