A nail is fixed at a point `P` vertically below the point of suspension 'O' of simple pendulum of length `1 m`. The bob is released when the string of pendulum makes an angle `30^@` with horiozontal. The bob reaches lowest point and then describes vertical circle whose centre coincides with `P` . The least distance of `P` from `O` is

Options

A. `0.4 m`
B. `0.5 m`
C. `0.6 m`
D. `0.8 m`

Answer

D

Explanation

If `v` is velocity at the lowest point
`v^(2) = 2gL (1-sin theta)` but, `v^(2) = 5gr & r = L -x`
where `x` is minimum distance between `0` and `P`.