1. What force does the most work? (A) 10 N force (B) 8 N force (C) 6 N force (D) They all do the same amount of work 2. As you ride an elevator going upward at constant speed, the work done on you by the normal force from the floor of the elevator is (A) Negative (B) zero (C) positive (D) Negative, zero or positive depending on the speed of the elevator 3. A car of mass 1,500 kg accelerates from rest. The net force on the car is as shown. What is the work done on the car by the net force after it has traveled a distance of 200 m? 4. A runner of mass 80 kg passes point A with a speed of 5.0 m/s. A second runner twice as heavy passes point A with half the speed of the first runner. Which of them has the larger kinetic energy? 5. A 30 N chest initially at rest was pulled 5.0 m across a smooth floor by applying a force of 50 N at an angle of 30". (a) How much work was done by tension Fr? FT 30 (b) What is the net work done on the object? (c) What is the acceleration of the chest? (d) What is the final speed of the chest? (e) What is the change in the kinetic energy of the chest. Is it equal to the net work found earlier?6. Bullet 1 is half the mass of bullet 2. Both bullets are fired so that they have the same speeds. If the kinetic energy of bullet 1 is K, the kinetic energy of bullet 2 must be (A) 2K (B) K/2 (C) 4K (D) K/4 (E) K (F) Kv2 7. The speed of a 2.5-kg mass changes from 15 m's to 35 m/'s. Determine the net work done on this mass. 8. A 2.5-kg mass moves at a constant speed of 35 m's over a distance of 150 m. Determine the net work done on this mass 9. What is the net work done on an object moving with constant velocity? (A) Positive (B) Negative (C) Zero 10. A 3.00 kg block is set into motion up an inclined plane with an initial speed of 8.00 m's. The block comes to rest after traveling 2.50 m along the inclined plane as shown in the figure. Determine the change in the potential energy of the block. 2.5 m 30-1 1. Christine runs forward with her sled at 2.0 m/s. She hops onto the sled at the top of a 3.0-m -high, very slippery slope. What is her speed at the bottom? 12. An object of mass 5.2 kg is at rest on an inclined plane as shown in the diagram below. (a) What is its potential energy? 8.7 m 20 (b) If the object is released from rest and slides down the inclined plane, what is its speed at the bottom? (c) If the plane was rough, and the object reaches the bottom of the plane with v = 5.5 m/'s, how much work was done by friction? 13. A dart gun with a spring constant k = 400.0 N/m is compressed 8.0 cm. (a) How much energy will it transfer to a dart of mass 200 g when the spring is released? (b) What would be the escape speed of the dart?13. A dart gun with a spring constant k = 400.0 N/m is compressed 8.0 cm. (a) How much energy will it transfer to a dart of mass 200 g when the spring is released? (b) What would be the escape speed of the dart? 3 (c) If the dart was aimed upward, how high would it travel? 14. How much electrical energy will a 40-watt light bulb use if left lit for 2 hours? [ 1 hour = 3,600 s] 15. A hot plate used 225,000 J of electrical energy in 5 minutes. What is the power (wattage) of the hot plate