5. Sally and Tammy are playing Roller Derby on opposite teams. Sally has a mass of 55kg and Tammy has a
mass of 49kg. Sally skates towards Tammy with a velocity of 15m/s and pushes her forward. Tammy,
who was originally skating with a velocity of 8.6m/s, is flung forward and finds herself with a velocity of
18.8m/s. What is Sally's velocity after they collide?