Two pendulums of lengths 1.44 m and 1 m start to swing together. The number of vibrations after which they will again start swinging together is

Options

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

Answer

D

Explanation

If t is the time taken by pendulums to come in same phase again first time after `t=0`.
Then, `(n+1)2pisqrt((l_(1))/(g))=n2pisqrt((l_(2))/(g))`
`(n-1)xxsqrt(1.44)=n`
`(n-1)=1.2n`
`(n+1)=1.2n`
`n=(1)/(0.2)=5`