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小 發表於 2016-1-31 09:26 PM (第 3002 天)
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Q14)
When you are walking forward, the direction of the friction from the ground acting on you is also pointing forward.
Your answer is True.
However,
If a man is walking forward with constant velocity, the net friction is zero ( If you dont count air resistance).
If a man is decelerating, the friction on him should be backwards.