AP Physics 1 Question 383: Answer and Explanation

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Question: 383

1. A box with a mass of 2 kg is placed on an inclined plane that makes a 30° angle with the horizontal. What must the coefficient of static friction (μs) between the box and the inclined be in order for the box to be at rest?

  • A. 0.5
  • B. 0.58
  • C. 0.87
  • D. 1

Correct Answer: B



There are free forces acting on the box: the weight of the box, the normal force of the inclined plane on the box, and the force of friction. The weight of the box can be separated into its parallel and perpendicular components.

In order for the box to be at rest, the net force in both the parallel and perpendicular directions must be zero: