A ball of mass 0.1 kg collides elastically with a ball of unknown mass at rest. If 0.1 kg ball rebounds at 1/3 of original speed, find the mass of another ball.

Explanation

`v_(1)=((m_(1)-m_(2))u_(1))/(m_(1)+m_(2))`
(Given `m_(1)=0.1kg,u_(1)=uandv_(1)=(-u)/(3)`)
`therefore (-u)/(3)=((0.1-m_(2))/(0.1+m_(2)))u`
`-u(0.1+m_(2))=3u(0.1-m_(2))`
`-m_(2)u+3m_(2)u=0.3u+0.u`
`2m_(2)u=0.4u`
`therefore m_(2)=(0.4)/(2)=0.2`
`therefore` Mass of other ball = 0.2 kg