Posted by sara on Sunday, March 28, 2010 at 9:03pm.
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?

physics  drwls, Monday, March 29, 2010 at 12:33am
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