A body of mass m hangs at one end of a string of lenth l, the other end of which is fixed. It is given a horizontal velocity so that the string would just reach where it makes an angle of `60^(@)` with the vertical. The tension in the string at bottommost point position is

Options

A. 2 mg
B. mg
C. 3 mg
D. `sqrt3mg`

Answer

A

Explanation

When body is released from the position p (inclined at angle `theta` from vertical), then velocity at mean positon
`v=sqrt(2gl(1-costheta))`
`therefore"Tension at the lowest point = mg"+(mv^(2))/(l)`
`=mg+(m)/(l)[2gl(1-cos60^(@))]=mg+mg=2mg`