P100Lec5 - physics1.usc.edu

Chapter 6, example #1 A baseball of a mass m = 0.2 kg falls vertically downward with a speed of v = 40 m/sec into the glove of a ball player. What is the impulse that is necessary to bring the ball to a stop? It the ball is stopped in 0.04 sec, what is the average force experienced by the hand of the ball player? Ans: 8 kg-m/sec and 200 N. Chapters 6 & 7, example #1

What would be the speed of a ball, which was at rest initially, falling from the top of a building of height 80 m when it hits the ground? What is the momentum of the ball when it hits the ground if the mass of the ball is m = 0.2 kg? What is the kinetic energy of the ball when it hits the ground? Assume the total mechanical energy is conserved. Ans: 40 m/sec, 8 kg-m/sec, and 160 J Chapter 7, example #1

How much work is required to lift a furniture of mass m = 40 kg from the ground up to a stair of 10 m high? What is the power dissipated if the lift takes 20 sec? Ans: 4000 J and 200 W.