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)/(2)m//s`
B. 2m/s
C. `(1)/(2)m//s`
D. 3m/s

Answer

B

Explanation

According to the law of conservation of energy
`TE_(at""L) = TE_(at""h)`
`(1)/(2)mv^(2) = (1)/(2)"mu"^(2) + mgh`
`v^(2) = u^(2) + 2gh or u^(2) = v^(2) - 2gh`
` u^(2) = 9 - 2 xx 10 xx (1)/(2)(1-(1)/(2))`
`u^(2) = 9 - 5 = 4`
` u=2 ms^(-1)`