A 10-grams stone is shot horizontally at a 2.0-kg wooden block hooked to a relaxed 200 N/m spring (the other end of the spring is fixed against a wall, the spring and the block sitting on a horizontal frictionless table). It is observed that the stone bounces back at 10 m/s and that the block compresses the spring by 4.0 cm. You are dealing here with an inelastic collision (when total momentum is conserved) followed by a spring compression (when mechanical energy is conserved),
a) What was the speed of the block right after the stone bounces off the block?
b) What was the speed of the stone just before collision?