AP Physics 1 Question 15: Answer and Explanation

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Question: 15

5. A ball of mass is attached to a string connected to the ceiling, forming a pendulum. When the string is raised to an angle of 50 degrees below the horizontal (the ceiling) and released, the ball swings back and forth with a period of 0.4 s. Which of the following changes to the pendulum would decrease the period of the pendulum?

  • A. Increasing the mass of the ball
  • B. Decreasing the length of the string
  • C. Decreasing the angle of the string from the horizontal when released
  • D. Decreasing the mass of the ball

Correct Answer: B


B The equation for the period of a pendulum is:

From this equation, it can be observed that changing the mass or the displacement angle of the pendulum will have no effect on the period. Decreasing the length of the string will lead to a decrease in the period.