AP Physics 1 Question 76: Answer and Explanation

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Question: 76

6. A box of mass m is sitting on an incline of 45° and it requires an applied force f up the incline to get the box to begin to move. What is the maximum coefficient of static friction?

  • A.
  • B.
  • C.
  • D.

Correct Answer: A


A The force of static friction and the force of gravity are acting down the incline in this situation. When the box just begins to move upwards the forces in both directions are equal and the force of static friction is at its maximum. Therefore, you have the equation

F = μsmg cos (45°) + mg sin (45°) → μs = – 1