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

Answer

B

Explanation

By the law of conservation of energy
`TE_(atL)=TE_(ath)`
`(1)/(2)mv^(2)=(1)/(2)m u^(2)+mgh`
`v^(2)=u^(2)+2gh`
`u^(2)=v^(2)-2gh`
`u^(2)=9-2xx10xx(1)/(2)`
`u^(2)=9-5=4`
`u=2m//s`