An 7.95 g bullet is fired horizontally into a 9.03 kg block of wood on an air table and is embedded in it. After the collision, the block and bullet slide along the frictionless surface together with a speed of 11.6 cm/s. What was the initial speed of the bullet?

Answer 1

Use the law of conservation of momentum to relate the velocity V' of the block (with embedded bullet) after impact, and the velocity of the bullet before impact, V.
0.00795 V = (9.03 + 0.0008)*V'

You already know V'. Solve for V.