A stone attached to a string is rotated in a vertical circle such that when it is at the top of the circle its speed is `V` and there is neither tension nor slacking in the string. The speed of stone when its angular displacement is `120^@` from the lowest point is

Options

A. `(3)/(2) V`
B. `sqrt(2) V`
C. `sqrt(3) V`
D. `sqrt((3)/(2)) V`

Answer

B

Explanation

`(mv^(2))/(r) = mg rArr v^(2) = gr`
If `theta` is angle from highest point
`v_(theta)^(2)-v^(2) =2g t(1-cos theta)`.