Question

A simple pendulum osscilates with an average period of 1.25 sec . determine it's length

Answer 1

A period of a simple pendulum is given by the following equation:

$$T = 2\pi\sqrt{\dfrac{l}{g}}$$

where $l$ is the length of the pendulum and $g = 9.81m/s^2$ is the gravitational acceleration. Expressing $l$, obtain:

$$l = \dfrac{T^2g}{4\pi^2} = \dfrac{1.25^2\cdot 9.81}{4\pi^2} \approx 0.39m$$

Answer. 0.39m.