physics
posted by sara .
A ball of mass 0.075 kg is fired horizontally into a ballistic pendulum. The pendulum mass is 0.350 kg. The ball is caught in the pendulum, and the centerof mass of the system rises a vertical distance of 0.145 m in the earth's gravitational field. What was the original speed of the ball? Assume g=9.80 m/s^2. How much kinetic energy was lost in the collision?

The distance than the block rises with the ball inside will tell you the velocity right after impact (V2), using conservation of energy.
V2 = sqrt (2gH); H = 0.145 m
Once you have determined V2, get the original speed of the ball (V1) by using conservation of momentum.
m V1 = (M+m) V2
Once you know v and V, calculatring the loss of kinetic energy is easy.
KE loss = (1/2)m V1^2  (1/2)(m+M)V2^2