You find it slightly easier to push a heavy box that is ALREADY MOVING than to start it from rest. The BEST explanation is:
ASliding friction is slightly smaller than static friction, because moving surfaces have less time to interlock
BThe box becomes lighter once it starts moving
CGravity decreases when the box moves
DAir resistance helps push the box once it moves
Answer & Solution
Correct answer: A. Sliding friction is slightly smaller than static friction, because moving surfaces have less time to interlock
Static friction is the limiting friction that must first be overcome to start the box moving. Once it slides, the surface irregularities cannot lock fully into each other, so sliding friction is slightly less. The box's weight doesn't change; gravity is constant; air resistance is negligible for a slow indoor push.
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