AP Physics 1 Question 385: Answer and Explanation

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Question: 385

3. A box with a mass of 5 kg is sliding across a table at a speed of 2 m/s. The coefficient of kinetic friction between the book and table is μ = 0.25. What is the minimum force that has to be applied on the box to maintain this speed?

  • A. 0 N
  • B. 10 N
  • C. 12.5 N
  • D. 25 N

Correct Answer: C

Explanation:

C

The minimum force exerted to maintain the speed of 2 m/s will result in no acceleration. Thus, the force required will result in Fnet = 0. The friction force acting against the motion is

Thus, the force required to maintain the speed is 12.5 N, just enough to counteract the friction force.