Two simple pendulums have time periods `T` and `5T//4`. They start vibrating at the same instant from the mean position in the same phase. The phase difference between them when the pendulum with higher time period complets one oscillation is

Options

A. 4T
B. 3T
C. 6T
D. 5T

Answer

C

Explanation

Let the two pendulums be again in phase after an elapse of time t. Then during this time t, if the pendulum of time period T makes n vibrations, the pendulum of time period `(5T)/(4)` will make `(n-1)` vibrations. So,
`t=nT=(n-1)(5T)/(4)or4n=5n-5orn=5 therefore t=5T`