A girl on the swing throws a ball at the velocity of positive +7.5 m/s relative to the swing. When the ball leaves her hand, the girl has a velocity of +13.5 m/s relative to the ground. What is the velocity of the ball relative to the ground when she throws it?
Because she's moving forward at the time and is throwing the ball in the same direction she's moving the ball goes faster than she does. so all you have to do is add 7.5 and 13.5 together and get 21 m/s
