Chapter 5, Energy 56 C HAPTER 5 5.1 Work 1. The unit of work, joule, is dimensionally the same as: a. newton/second. b. newton/kilogram. c. newton-second. d. newton-meter. 2. Rupel pushes a box 5.00 m by applying a 25.0-N horizontal force. What work does she do? a. 10.0 J b. 25.0 J c. 125 J d. 550 J 3. A worker pushes a sled with a force of 40 N over a level distance of 6.0 m. If a frictional force of 24 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow? a. 240 J b. 216 J c. 144 J d. 96 J 4. A horizontal force of 100 N is applied to move a 45-kg cart across a 9.0-m level surface. What work is done by the 100-N force? a. 405 J b. 500 J c. 900 J d. 4 500 J 5. I use a rope 2.00 m long to swing a 10.0-kg weight around my head. The tension in the rope is 20.0 N. In half a revolution how much work is done by the rope on the weight? a. 40.0 J b. 126 J c. 251 J d. 0
Chapter 5, Energy 57 6. The work done by static friction can be: a. positive. b. negative. c. zero. d. Any of the above. 7. A satellite is held in orbit by a 2 000-N gravitational force. Each time the satellite completes an orbit of circumference 80 000 km, the work done on it by gravity is: a. 1.6 x 10 8 J. b. 1.6 x 10 11 J. c. 6.4 x 10 11 J. d. 0. 5.2 Kinetic energy and the Work-Energy Theorem 8. Which of the following is an example of a nonconservative force? a. gravity b. magnetism c. friction d. Both choices A and B are valid. 9. Which of the following is that form of energy associated with an object’s motion? a. potential b. thermal c. bio-chemical d. kinetic 10. Which of the following is that form of energy associated with an object’s location in a conservative force field? a. potential b. thermal c. bio-chemical d. kinetic 11. What is the kinetic energy of a 0.135-kg baseball thrown at 40.0 m/s (90.0 mph)? a. 54.0 J b. 87.0 J c. 108 J d. 216 J
Chapter 5, Energy 58 12. A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface. If the cart accelerates at 2.0 m/s 2 , then what is the work done by the force of friction as it acts to retard the motion of the cart? a. -1 100 J b. -900 J c. -800 J d. -700 J 13. A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision? a. 1/4 b. 3/8 c. 7/16 d. 9/16 14. If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of: a. 3. b. 6. c. 9. d. 27. 15. A 1 200-kg automobile moving at 25 m/s has the brakes applied with a deceleration of 8.0 m/s 2 . How far does the car travel before it stops? a. 39 m b. 47 m c. 55 m d. 63 m 16. If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object’s kinetic energy? a. decreases
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