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. `sqrt2V`
C. `sqrt3V`
D. `sqrt3/2 V`

Answer

`(2)`

Explanation

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