A bullet of mass 20 g strikes a pendulum of mass 5kg. The centre of mass of pendulum rises a vertical distance of 10 cm. If the bullet gets embedded into the pendulum, calculate its initial speed.

Explanation

Mass of the bullet
`m=20g`
Mass of the bob
`M=5kg`
Height `h=10cm`
To find initial velocity
`u=??`
Formula: Law of conservation of momentum:
`m u+0=(M+m)v" "...(1)`
Law of conservation of energy
`(1)/(2)(M+m)v^(2)=(M+m)gh" "...(2)`
`therefore v=sqrt(2gh)" "...(3)`
(3) in (1)
Initial speed, `u=((M+m)sqrt(2gh))/(m)`
`=(sqrt(2xx9.8xx0.1)/(0.02))xx5.02`
`implies351.4m//s`