Question

Someone fires a 0.04 kg bullet at a block of wood that has a mass of 0.5 kg. The block of wood is sitting on a frictionless surface, so it moves freely when the bullet hits it. The wood block is initially at rest. The bullet is travelling 300 m/s when it hits the wood block and sticks inside it. Now the bullet and the wood block move together as one object. How fast are they traveling?

Answer 1

The momentum of the wood and the bullet is equal to the momentum of the bullet before it hits the wood
0.04 x 300 = 12 kg m/s
(0.5 + 0.04)*v = 12 kg m/s,
v = 12 kg m/s / 0.54 kg = 22.2 m/s