A railway flat car, whose mass together with the artillery gun is `M = 2 m`, moves at a speed `V`. The gun barrel makes an angle `alpha = 60^(@)` with the horizontal. A shell of mass `m` leaves the barrel at a speed `v = 12 ms^(-1)`, relative to the barrel. Find the speed of the flat car `V` (in `ms^(-1)`) in order that it may stop after the firing.

Answer

2

Explanation

Using conservation of linear mometum
`(2m+m)V=2mxx0+mvcosalpha`
`V=(mvcosalpha)/(3m)=1/3vcosalpha=1/3xx12xxcos60^(@)=2ms^(-1)`