A bead is free to slide down a smooth wire tightly stretched between points A and on a verticle circle of radius R. if the bead starts from rest at 'A', the highest point on the circle, its velocity when it arrives at B is :-

Options

A. `2sqrt(gR)`
B. `2sqrt(gR) cos theta`
C. `(2sqrt(R))/(g)`
D. None of these

Answer

B

Explanation

`a=g costheta`
`AB=2Rcos thetarArrv^(2)=u^(2)+2as`

`v^(2)=0+2(g cos theta)xx2Rcos theta rArr v^(2)=4gR cos ^(2)theta`
`rArrv=2sqrt(gR) cos theta`