Question

why does a gun recoil on firing obtain an expression for recoil velocity of gun

Answer 1

according to newton's third law of motion every force (action) has an opposite and equal reaction.

therefore, a gun always recoils on firing m = mass of bullet M = mass of gun u = initial velocity of bullet=0 (since, gun is at rest) U= initial velocity of gun= 0(since, gun is at rest) v =final velocity of bullet V=final velocity of gun conservation of mometum formula mu + MU = mv + MV since u and U = 0 therefore, recoil velocity= mv + MV => MV = -mv => V = -mv/M .