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Chapter 11 Homework Physics 1. A compact car has a mass of 750.0 kg. (a) What is the kinetic energy of the car if it is moving at 50.00 km/hr? (b) How much work is done on the car to accelerate it from 50.00 km/hr to 100.0 km/hr? (c) How much work is done on the car to bring it from 100.0 km/hr to rest? (d) What average force is exerted on the car if it has a stopping distance of 500.0 meters? 2. A rifle can shoot a 4.20 gram bullet at a speed of 965 m/s. (a) What is the kinetic energy of the bullet when it leaves the rifle? (b) How much work is done on the bullet if it starts from rest? (c) If the bullet is fired into an anchored wooden block and stops before exiting the block, how far into the block does it stop if the block exerts an average force of -135000 N? 3. A 90.0 kg rock climber ascends 45.0 meters up to the top of a quarry, then descends 85.0 meters from the top of the quarry to the ground. (a) Find the potential energy of the climber at the top relative to his starting position. (b) Find the potential energy of the climber at the bottom relative to his starting position. 4. A carpenter carries a 1.00 kg hammer up a ladder to a height of 5.00 meters. He then accidentally drops the hammer, and it falls to the ground. (a) Find the potential energy of the hammer at a height of 5.00 meters. (b) Find the potential energy of the falling hammer when it reaches a height of 2.00 meters. (c) Find the kinetic energy of the falling hammer when it reaches a height of 2.00 meters. (d) Find the velocity of the falling hammer when it reaches a height of 2.00 meters. (e) Find the kinetic energy of the falling hammer just before it hits the ground. (f) Find the velocity of the falling hammer just before it hits the ground. 5. A bicyclist approaches a hill with a speed of 8.50 m/s. The total mass of the bicycle and the rider is 85.0 kg. (a) What is the total kinetic energy of the bicycle and the rider as she approaches the hill? (b) Ignoring friction, if the bicycle coasts up the hill, at what height does it come to a stop? 6. Tarzan, with a mass of 75.0 kg, swings down from a tree limb on the end of a vine. His feet touch the ground 4.00 meters below the tree limb. (a) Find Tarzan’s potential energy relative to the ground when he stands on the tree limb. (b) Find Tarzan’s speed when his feet touch the ground. 7. A 60.0 kg skier starts from rest at the top of a 45.0 meter hill and skis down a 30 degree incline into a valley. He then continues up a 40.0 meter hill. The height of each hill is measured vertically from the bottom of the valley, and the skier does not use poles. (a) What is the skier’s potential energy at the top of the first hill relative to the bottom of the valley? (b) Ignoring friction, what is the skier’s kinetic energy at the bottom of the valley? (c) How fast is the skier moving at the bottom of the valley? (d) What is the skier’s potential energy at the top of the second hill? (e) Ignoring friction, what is the skier’s kinetic energy at the top of the second hill? (f) How fast is the skier moving at the top of the second hill? 8. A 2.00 gram bullet moving with a velocity of 538 m/s strikes a 0.250 kg piece of wood initially at rest on a frictionless table. The bullet is embedded in the wood. (a) Find the velocity of the bullet-block system after the collision. (b) Find the total kinetic energy of the bullet-block system before the collision. (c) Find the total kinetic energy of the bullet-block system after the collision. (d) Is the collision elastic, inelastic, or completely inelastic? 9. A 0.15 kg cue ball with a velocity of 0.90 m/s strikes a second 0.15 kg billiard ball initially at rest on a frictionless table. After the collision, the cue ball stops. (a) Find the velocity of the other billiard ball after the collision. (b) Find the total kinetic energy of the system before the collision. (c) Find the total kinetic energy of the system after the collision. (d) Is the collision elastic, inelastic, or completely inelastic? 10. A 615 kg car traveling with a velocity of 18.0 m/s collides with a 1550 kg car moving in the same direction with a velocity of 5.00 m/s. After the collision, the second car moves with a velocity of 9.00 m/s. Ignore friction between the tires and the road. (a) Find the velocity of the first car after the collision. (b) Find the total kinetic energy of the system before the collision. (c) Find the total kinetic energy of the system after the collision. (d) Is the collision elastic, inelastic, or completely inelastic? 11. A 2.00 kg puck moving with a velocity of 4.00 m/s on a frictionless surface collides with a 3.00 kg puck moving in the opposite direction with a velocity of -1.00 m/s. The collision is elastic. (a) Find the velocity of the 2.00 kg puck after the collision. (b) Find the velocity of the 3.00 kg puck after the collision.