60 kg shell flying at a speed of 20 m/s explodes into two pieces. If one piece of mass 25 kg stops, then the velocity of the other piece will be.

Mass of the shell, M = 60 kg

Speed of the shell, u = 20 m/s

Initial momentum of the shell, Pi = Mu = (60) x (20) = 1200 kg-m/s

After it breaks, the masses of the parts are 25 kg and 35 kg. The 25 kg piece stops. Let the speed of the other piece be ‘v’.

So, total momentum after breaking apart, Pf = (25)(0) + (35)(v) = 35v

Now, by law of conservation of momentum, Pf = Pi

=> 35v = 1200

=> v = 1200/35 = 34.3 m/s

This is the speed of the other piece.