A simple pendilum with bob of mass m and length l is held in position at an angle `theta` with t he verticle. Find its speed when it passes the lowest position.

Explanation

During motion of pendulum from A to B, its potential energy will convert into kinetic energy.

The height pendulum comes in downward direction is BC
and `BC=SB-SC=L-L cos theta`
By law of conservation of mechanical energy,
`mgh=(1)/(2)mv^(2)`
`rArr" "mg[L-L cos theta]=(1)/(2)mv^(2)`
`rArr" "v=sqrt(2gL[1-cos theta])`