A bullet of mass 5.2 g is fired horizontally into a 7.1 kg wooden block at rest on a horizontal surface. The coefficient of kinetic friction between block and surface is 0.50. The bullet stops in the block, which slides straight ahead for 1.5 m (without rotation).
(a) What is the speed of the block immediately after the bullet stops relative to it?
(b) At what speed is the bullet fired?