A pendulum bob has a speed of `3ms^(-1)` at its lowest position. The pendulum is `0.5` m long. The speed of the bob, when string makes an angle of `60^(@)` to the vertical is `("take, g"=10ms^(-1))`

Options

A. `3 ms^(-1)`
B. `1//3 ms^(-1)`
C. `1//2 ms^(-1)`
D. `2 ms ^(-1)`

Answer

D

Explanation

`(1) /(2) mv^(2) +mg l (1- cos theta )=(1)/(2) mv ^(2)`
` or v^(2) + 2gl(1- cos theta ) = v^(2) `
` or v^(2) + 2xx10xx0.5(1-(1)/(2))=9`
` or v^(2) = 9-5=4`
`or v=2 ms ^(-1)`