Question

Two ball bearings of mass m each moving in opposite directions with same speed v collide head on with each other. If the collision is perfectly elastic, what will be the outcome of the collision ?

Answer 1

Here, `m_(1)=m_(2),u_(1)=v,u_(2)=-v`
`:.v_(1)=((m_(1)-m_(2))u_(1)+2m_(2)u_(2))/((m_(1)+m_(2)))`
`=((m-m)u_(1)+2m(-v))/(2m)=-v`
and `v_(2)=((m_(2)-m_(1))u_(2)+2m_(1)u_(1))/(m_(1)+m_(2))`
`=((m-m)(-v)+2mv)/(2m)=v`
Hence after collision, the two ball bearings will move with same speed, but their directios of motion are reversed.