Raindrop if - 0 m/s Given: m/ 4t = 0.060 kg/s Vo = - 15 m/s v/ = 0 m/s Required: F = the average force exerted by the rain on the roof. Solution: F =- mv - mv. At At F =-(0.060kg/s)-15m/s)=+0.90N This force is in the positive or upward direction, which is re force on each falling drop in order to bring it to reck erted on the roof by the rain also hasa Fortitude of 0.90 1.90 N 4.2 The Impulse-Momentum Equation 7. An impulse of 7.5 x 10' N's stops a car in 0.10s. (a) Calculate the average force on the car. (b) If the impulse time is tripled, what is the average force on the car? 8. A 2.0 x 105-N friction force caused by the brakes of a subway train stops the train in 50 s. (a) Calculate the force needed to stop the train in 25 s. (b) Calculate the stopping time if a 1.0 x 105-N friction force acts on the train. 9. About 80 g of blood is pumped from the heart during each heartbeat. The blood starts at rest and has a speed of about 0.6 m/s in the aorta. If the pumping takes 0.17s, what is the magnitude of the average force on the blood? . 10. A 0.60-kg basketball falling vertically at a speed of 6.0 m/s hits a floor and rebounds at a speed of 5.2 m/s. (a) Calcu- late the ball's change in momentum (magnitude and direction)