To double the period of a pendulum, you need to multiply its length by a factor of:
A) $\frac{1}{2}$
B) 2
C) $\sqrt{\frac{1}{2}}$
D) $\sqrt{2}$
E) 4
F) Some other result (specify)

Question

Quizplus · Accepted Answer

The period of a pendulum is given by $T = 2\pi\sqrt{\frac{L}{g}}$, where $L$ is the length of the pendulum and $g$ is the acceleration due to gravity. To double the period, the new period $T'$ is $2T$, so $2T = 2\pi\sqrt{\frac{L'}{g}}$. Solving for $L'$ in terms of $L$ gives $L' = 4L$, meaning the length must be multiplied by 4.

To Double the Period of a Pendulum, You Need to Multiply