How Everything Works
How Everything Works How Everything Works

Question 42

If Newton's third law is true - then how can you move anything? If it exerts the exact same amount of force on you that you exert on it, wouldn't the net force be zero and the object wouldn't move?
The total force on the two of you (the object you're pushing on and you yourself) would be zero, but the object would be experiencing a force and you would be experiencing a force. As a result, the object accelerates in one direction and you accelerate in the other! To see this, imaging standing on a frozen pond with a friend. If the two of you push on one another, you will both experience forces. You will push your friend away from you and your friend will push you in the opposite direction. You will both accelerate and begin to drift apart. Each of you individually will experience a net force. (It's true that the two of you together will experience zero net force, which means that as a combined object, you won't accelerate. The way this appears is that your overall center of mass won't accelerate. It will remain in the middle of the pond even as the two of you travel apart toward opposite sides of the pond.)

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