A grenade flying at a speed of 10 m / s exploded into two pieces weighing 0.6 kg and 0.4 kg.

A grenade flying at a speed of 10 m / s exploded into two pieces weighing 0.6 kg and 0.4 kg. The speed of the larger fragment increased to 25 m / s. Find the speed of the smaller shard.

Given: Vg (speed of the grenade before rupture) = 10 m / s; mb (the mass of most of the grenade) = 0.6 kg; mm (mass of the smaller part) = 0.4 kg; Vb (velocity of the larger fragment) = 25 m / s.

The speed of a smaller fragment of a grenade is determined using the law of conservation of momentum: m * Vg = (mb + mm) * Vg = mb * Vb + mm * Vm and Vm = ((mb + mm) * Vg – mb * Vb) / mm.

Let us calculate: Vm = ((0.6 + 0.4) * 10 – 0.6 * 25) / 0.4 = (10 – 15) / 0.4 = -12.5 m / s (the and larger pieces are oppositely directed).