In inelastic collision the law of conservation of momentum holds good, but the law of conservation of kinetic energy doesn't hold good. Collisions in our day-to-day life are examples for inelastic collisions.

Consider two bodies A and B of masses m₁ and m₂ moving along a straight line with velocities u₁ and u₂ respectively. They collide each other. They remain in contact for some time ad then gets separated. After collision let their velocities v₁ and v₂ respectively along the same straight line.

According to the law of conservation of momentum, total momentum before collision = total momentum after collision.

If m₁ = m₂ = m and u₂ = 0, then v₁ = (1 – e)(u₁/2) and v₂ = (1 + e)(u₁/2)

Loss in kinetic energy of the sytem in inelastic collision is