Consider a quarter circular smooth rod AB fixed AB fixed in a vertical plane with centre of the circle at O. A bead of mass m slides without friction with the help of string starting from point A under the action of a constant force `F = 2 gm` as shown in figure.

Work done by force F up till the moment when bead reaches at position B is : (Take `m = sqrt(2kg)` )

Options

A. `100 J`
B. `200 J`
C. `400 J`
D. `50 J`

Answer

C

Explanation

`W_(F) = (2 mg) (sqrt2R)`