Question

A simple pendulum swings with a period of 1.5 s. What would be the period of the pendulum if the length of its string was doubled, the mass of its bob were cut in half, and the force of gravity was doubled?

• A. 0.5 s
• B. 1.5 s
• C. 3 s
• D. Can’t be determined

Answer 1

The correct option is B

1.5 s

The mass of a pendulum’s bob has no effect on its period, so this change is irrelevant. Multiplying the length of the string by two would multiply the period of the pendulum by the square root of two. Multiplying the force of gravity by two would divide the period of the pendulum by the square root of two. Together, those two changes cancel each other out. Therefore, the pendulum would have exactly the same period that it had before, i.e., 1.5 seconds.