posted by Lucas .
A bullet whose mass is 0.0015kg leaves a 5kg leaves a 5kg rifle at a muzzle velocity of 800 m/s. It strikes a 7kg block of wood and becomes embedded in it.
After the bullet hits the rock, what is the speed of the bullet/ block system?
preserve momentum, so
(0.0015)(800) = (0.0015+7)v