Physics- momentum problem?

A small object with a momentum of magnitude 5.0 kg m/s approaches head-on a large object at rest. The small object bounces straight back with a momentum of magnitude 4.0 kg m/s. What is the magnitude of the small object's momentum change in kg m/s? 2. A 0.060-kg tennis ball, initially moving at a speed of 12 m/s, is struck by a racket causing it to rebound in the opposite direction at a speed of 18 m/s. What is the change in momentum of the ball in kg m/s? A bullet of m m1 is fired with a speed v into the wooden bob of a pendulum having m m2. The bob is attached to a very light rigid rod of length L that is pivoted at the other end. (a) The bullet is stopped in the bob. How high will the bob rise? (b) A narrower bob with the same m is used instead of the original one. This time, the bullet pes through the bob, emerging with a speed v/2. Now how high will the bob rise?