A girl on inline skates is traveling to the left at 0.5 m/s. Her mass is 30 kg. A ball of mass 2.0 kg is traveling to the right at 2.5 m/s. The girl catches the ball and holds on to it. All motion is measured relative to the ground. Ignore friction.

a) What is the girl's velocity after she catches the ball? Consider motion to the left to be negative and motion to the right to be positive.

b) The girl then throws the ball away from herself, so that the ball has a velocity of 1.5 m/s to the left. What is the girl's velocity after she throws the ball? Consider motion to the left to be negative and motion to the right to be positive.