A gum (mass=M) fires a bullet (mass=m) with speed `v_r` relative to barrel of the gum which is inclined at an anlge of `60^@` with horizontal. The gun is placed over a smooth horizontal surface. Find the recoil speed of gun.

Answer

B

Explanation

Let the recoil speed of gun is `v`. Taking gun + bullet as the system. Net external force on the system in horizontal direction is zero. Initially the system was at rest. Therefore, applying the principle of conservation of linear momentum in horizontal direction, we get

`Mv-m(v_r cos 60^@-v)=0`
`:. v=(mv_r cos 60^@)/(M+m)` or `v=(mv_r)/(2(M+m))`