MCAT Physics Question 15: Answer and Explanation

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Question: 15

15. Which of the following statements is true of movement on a plane with friction?

I. Acceleration is a function of applied force only.

II. More force is needed to accelerate a stationary object than a moving object.

III. The force of friction is independent of the mass of objects.

  • A. I only
  • B. II only
  • C. I and II only
  • D. I and III only

Correct Answer: B

Explanation:

The presence of friction does not change the impact of Newton's laws. A net force must still be applied to cause motion. This net force is not necessarily equal to an applied force, as friction and gravity also act on the object; thus, statement I is eliminated. Static friction opposes the movement of stationary objects, and is necessarily greater than the force of kinetic friction; thus, statement II is correct. Statement III is false because the normal force is related to mass, and friction is related to the normal force.

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