## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

$L = 0.54~m$
We can use the following equation for the period of a physical pendulum: $T = 2\pi~\sqrt{\frac{I}{mgl}}$ $T = 2\pi~\sqrt{\frac{\frac{1}{3}mL^2}{mg~(\frac{L}{2})}}$ $T = 2\pi~\sqrt{\frac{2L}{3g}}$ $L = \frac{T^2~(3g)}{2~(2\pi)^2}$ $L = \frac{(1.2~s)^2~(3)(9.80~m/s^2)}{2~(2\pi)^2}$ $L = 0.54~m$