Question

A railway flat car, whose mass together with the artillery gun is M $=$ 2m, moves at a speed V. The gun barrel makes an angle $\alpha ={60}^o$ with the horizontal. A shell of mass m leaves the barrel at a speed $v=12m{s}^{-1}$, 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 1

Given, intial velocity=V
and intial mass=3m
velocity at which shell of mass m is thrown =12m/s
angle=60
by applying law of conservation of momentum in horizontal direction,
intial horizontal momentum=final horizontal momentum.
$\left(3m\right)\left(V\right)=m\left(12\right)cos\left(60\right)+0$
$\Rightarrow V=2m/s$