I fire a bullet at a ballistic pendulum. The large block of wood has a mass M2 = 3.000 kg, and the bullet has a mass of m1 = 25.0 g. The bullet completely penetrates the wood and emerges with a speed of vf = 80.0 m/s. The wood, as part of a pendulum, swings up to a maximum height of h = 10.00 cm.
(a) Determine the speed of the block of wood after the bullet has passed through it.
(b) What is the speed of the bullet just before it hits the block?
The Attempt at a Solution
I thought that setting the momentum of the bullet after it has exited the block equal to the momentum of the block at the maximum height would be the correct procedure to find the speed of the block , but I am wrong. How do I approach this problem? Convervation of energy or conservation of momentum? Or both?