A simple pendulum oscillates in a vertical plane. When it passes through the mean position, the tension in the string is `3` times the weight of the pendulum bob.what is the maximum displacement of the pendulum with respect to the vertical

Options

A. `30^(@)`
B. `45^(@)`
C. `60^(@)`
D. `90^(@)`

Answer

D

Explanation

At mean position,
`mg+(mv^(2))/(r)=3mgrArrv=sqrt(2gl)`…..(i)
and if the body displace by angle `theta` with vertical, then
`v=sqrt(2gl(1-costheta))`……(ii)
On comparing Eqs. (i) and (ii), we get
`costheta=0rArrtheta=90^(@)`