AP Physics 1 Question 204: Answer and Explanation

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Question: 204

4. A 20 N block is being pushed across a horizontal table by an 18 N force. If the coefficient of kinetic friction between the block and the table is 0.4, find the acceleration of the block.

  • A. 0.5 m/s2
  • B. 1 m/s2
  • C. 5 m/s2
  • D. 7.5 m/s2

Correct Answer: C

Explanation:

C

The net force on the block is F - Ff = F - µkFN = F - µkFw = (18 N) - (0.4)(20 N) = 10 N. Since Fnet = ma = (Fw/g)a, you get 10 N = [(20 N)/(10 m/s2)]a, which gives a = 5 m/s2.