posted by Danisha .
Two boys standing on carts that move along a horizontal frictionless surface. The mass of each boy-cart combination is 100 kg, and each moves initially with the velocities of: Boy A 7cm/sec and Boy B: 10cm/sec. The boy on cart A throws a 2kg ball to the boy on Cart B (assume it travels horizontally). The boy on cart B then throws the ball at 15m/sec in the forward direction and finds that his cart has come completly to rest. At what speed must the boy on cart A have thrown the ball in order to make this happen?