A basketball bounces on a floor. The ball has a mass of 0.61 kg and is in contact with the floor for 0.015seconds. If the average total force acting on

the ball during contact with the floor is 300 N and the ball rebounds with a speed of 3.5 m/s, calculate the speed of the ball just before it hits the floor. What would the effect on the average force be if the contact time were to increase?