A10 1. A gas-powered winch on a rescue helicopter does 4200 J of work while lifting a 50 kg swimmer at a constant speed up from the ocean. Through what height was the swimmer lifted? 2. A weightlifter raises a loaded barbell 2.2 m. The lift increases the gravitational potential energy of the barbell by 490 J. Determine the mass of the loaded barbell. 3. A 2.5 kg piece of wood falls onto a carpenter's table from a height of 2.0 m above the table. 4. a. Calculate the kinetic energy of the wood as it hits the table? b. Calculate the speed of the wood as it hits the table? 2. What, relative to the ground, is the gravitational potential energy of a 62.5-kg visitor standing at the lookout level of Toronto's CN Tower, 346 m above the ground? 3. A 58.2-g tennis ball is dropped from rest vertically downward from a height of 1.55 m above the court surface. (a) Determine the gravitational potential energy of the ball relative to the court sur- face before it is dropped, and as it strikes the court surface. (b) How much work has the force of gravity done on the ball at the instant the ball strikes the court surface? (c) Relate the work done in (b) to the change in the kinetic energy from the release point to the court surface. 4. A 68.5-kg skier rides a 2.56-km ski lift from the base of a mountain to the top. The lift is at an angle of 13.9 to the horizontal. Determine the skier's gravitational potential energy at the top of the mountain relative to the base of the mountain. 5. A high jumper clears the pole at a height of 2.36 m, then falls safely back to the ground. The change in the jumper's gravitational potential energy from the pole to the ground is -1.65 103 J. Determine the jumper's mass. 6. On your desk you have N identical coins, each with a mass m. You stack the coins into a vertical pile to height y. (a) Approximately how much work, in terms of m, g, and y, must you do on the last coin to raise it from the desk to the top of the pile? (b) Approximately how much gravitational potential energy, in terms of m, g, N, and y, is stored in the entire pile?