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A simple pendulum of bob of mass m and l...

A simple pendulum of bob of mass `m` and length `L` has one of its ends fixed at the centre `O` of a vertical circle, as shown in the figure. If `0=60^(@)` at the point `P`, the minimum speed `u` that should be given to the bob so that it completes vetical circle is

A

`sqrt(gL)`

B

`sqrt(2gL)`

C

`sqrt(5gL)/(2)`

D

`sqrt(3gL)/(2)`

Text Solution

Verified by Experts

The correct Answer is:
B
Energy conservation at heighest point
`{v_("top")=sqrt(gR)}`
`(1)/(2)m u^(2)=(mgR)/(2)+(1)/(2)m(sqrt(gR))^(2)rArru=sqrt(2gR)`
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