Figure shows a light rod of length l rigidly attached to a small heavy block at one end and a hook at the other end. The system is released from rest with the rod in a horizontal position. There is a fixed smooth ring at a depth h below the initial position of the hook and the hook gets into the ring as it reaches there. What should be the minimum value of h so that the block moves in a complete circle about the ring?

Options

A. `h=L`
B. `h=2L`
C. `h=3L`
D. `h=4L`

Answer

A

Explanation

`mg(h+L)=(1)/(2)mv^(2)impliesv^(2)=2g(h+L)`
To complete the verticle circle about `O`,
`vgesqrt(4gL)`
`V^(2)ge4gL`
`2g(h+L)ge4gL`
`hgeL`
`h_(min)=L`