Cutnell/Johnson Physics 8 th edition

1. Cutnell/JohnsonPhysics 8th edition • Classroom Response System Questions Chapter 6 Work and Energy Reading Quiz Questions

2. 6.1.1. In which one of the following situations is zero net work done? a) a bunch of bananas are placed on a spring scale in the supermarket b) a sky diver falls from an airplane before opening her parachute c) a horse pulls a wagon at a constant velocity d) a snowball rolls down a hill e) a skateboarder steps on a skateboard and begins to roll

3. 6.1.2. Work may be expressed using all of the following units except: a) watt b) joule c) N  m d) erg e) ft  lb

4. 6.1.3. A 5.0-kg ball on the end of a chain is whirled at a constant speed of 1.0 m/s in a horizontal circle of radius 3.0 m. What is the work done by the centripetal force during one revolution? a) 2.5 J b) 1.7 J c) 1.2 J d) 0.56 J e) zero J

5. 6.1.4. Which one of the following is not a unit of energy? a) joule b) watt c) newton  meter d) kilowatt  hour e) foot  pound

6. 6.1.5. Which one of the following combinations of units is equal to the joule? a) kg  m2/s b) kg  m c) kg  m/s d) kg  m2/s2 e) kg  s

7. 6.1.6. In which one of the following circumstances does the force do positive work on the object? a) The direction of the force is perpendicular to the object’s displacement. b) The direction of the force is in the opposite direction to the object’s displacement. c) No matter the direction of the force, positive work will be done if there is a displacement of the object. d) The direction of the force is in the same direction as the object’s displacement. e) The object’s displacement is zero meters as the force is applied.

8. 6.2.1. Which one of the following statements concerning kinetic energy is true? a) The kinetic energy of an object is directly proportional to its speed. b) The kinetic energy of an object is expressed in watts. c) The kinetic energy of an object is a quantitative measure of its inertia. d) The kinetic energy of an object always has a positive value. e) The kinetic energy of an object is always equal to the object’s potential energy.

9. 6.2.2. Which one of the following is an example of an object with a non-zero kinetic energy? a) A train is parked in a train station. b) A car rests at the top of a hill. c) The pendulum of a grandfather clock is still. d) A boulder rests at the bottom of a cliff. e) The International Space Station orbits the Earth.

10. 6.2.3. In which one of the following situations will there be an increase in kinetic energy? a) A kicked football approaches its maximum height as it passes through the goal posts. b) The planet Venus moves in its nearly circular orbit around the Sun. c) A fan is switched from “low speed” to “high speed.” d) A filing cabinet is pushed across a rough floor at constant speed. e) A train is pulled up a mountain at a constant speed by a motor.

11. 6.2.4. Which one of the following expressions is equal to the kinetic energy of an object? a) mvt2 b) c) Fd cos  d) ma e) mgh

12. 6.2.5. Complete the following statement: If positive work is done on a moving object, a) the velocity of the object will increase. b) the velocity of the object will decrease. c) the kinetic energy of the object will decrease. d) the velocity of the object will not change. e) the direction of the acceleration of the object will be opposite to its displacement.

13. 6.3.1. In which one of the following systems is there a decrease in gravitational potential energy? a) A large boulder rests at the bottom of a steep hill. b) A helicopter takes off from the roof of a hospital and flies due west. c) A child accidentally releases a helium-filled balloon and it flies upward into the clouds. d) A girl jumps down from a bed and lands on her feet. e) A truck drives at an average velocity of 25 m/s, due north along a level, country road.

14. 6.3.2. A man carries a 12-kg chair up one flight of stairs to the second floor of his house. If the second floor is 3.3 m above the first floor, what is the change in the gravitational potential energy of the chair? a) 180 J b) +390 J c) +180 J d) 390 J e) +240 J

15. 6.3.3. An arrow is launched straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the arrow as it rises? Neglect air resistance. a) The kinetic energy of the arrow increases and its potential energy decreases. b) Both the potential energy of the arrow and its total energy increase. c) The kinetic energy of the arrow decreases as the potential energy increases. d) Both the kinetic energy of the arrow and its potential energy remain constant. e) The total energy of the arrow increases.

16. 6.3.4. An object is initially at height y1. After a time interval t, the object is located at height y2. The work done by the gravitational force on the object is dependent on which of the following quantities? a) y1y2 b) the path taken from y1 to y2 c) the time interval t taken to move from y1 to y2 d) choices a and b e) choices a and c

17. 6.3.5. Alice and Bill, who happen to have the same mass, both want to climb to the top of a mountain. Bill wants to take the steep path straight up, but Alice wants to take the path that gently winds around the mountain, even though it is 8 times longer than the steep path. They both eventually reach the top of the mountain, but Alice reaches the top in 1/3 the time that Bill takes using the steep route. How does the work that Alice did in climbing the mountain compare with the amount that Bill did? a) Alice did 1/8 the amount of work that Bill did. b) Alice did 1/3 the amount of work that Bill did. c) Alice and Bill did the same amount of work. d) Alice did twice the amount of work that Bill did. e) Alice did three times the amount of work that Bill did.

18. 6.3.6. Sara carries a heavy box of books down a flight of stairs from the third floor to the first floor. Which one of the following statements best describes the work done on the box by Sara? a) Sara doesn’t do any work on the heavy box of books. b) Sara does a small amount of negative work on the heavy box of books. c) Sara does a small amount of positive work on the heavy box of books. d) Sara does a large amount of negative work on the heavy box of books. e) Sara does a large amount of positive work on the heavy box of books.

19. 6.3.7. What is the relationship between the gravitational potential energy of an object and the work done on the object by the gravitational force? a) The work is equal to the gravitational potential energy. b) The negative of the work is equal to the change in the gravitational potential energy. c) The negative of the work is equal to the square of the gravitational potential energy. d) The work is equal to the square of the gravitational potential energy. e) The work is equal to one-half of the gravitational potential energy.

20. 6.4.1. Complete the following statement: A force that acts on an object is said to be conservative if a) the work it does on the object is equal to the increase in the object's kinetic energy b) the work it does on the object is independent of the path of the motion. c) it always acts in the direction of motion of the object. d) it results in a change in the object's kinetic energy. e) it obeys Newton's laws of motion.

21. 6.4.2. Which one of the following situations is an example of a conservative force acting? a) A boat motor produces a propulsion force that moves the boat across a lake. b) The tension force in the rope increased as the piano was lifted off the ground. c) A child jumping on a trampoline is pushed upward by an elastic spring force. d) A normal force pushes upward on a book as it sits on a table. e) The static frictional force between the tires of a car and the road.

22. 6.4.3. Which one of the following choices is an example of a non-conservative force? a) elastic spring force b) gravitational force c) kinetic frictional force d) electrical force

23. 6.4.5. Complete the following statement: The net work done by a conservative force acting on an object a) depends only on the time that the force is exerted. b) depends only on the velocity of the object. c) depends only on the starting and ending points. d) is always equal to zero joules. e) is always greater than zero joules.

24. 6.4.6. A ball is constrained to follow a circular path by a conservative force. During a time interval t, the ball makes exactly one revolution.Which one of the following statements concerning the net work done on the ball during time t is true? a) The net work depends only on the time t. b) The net work depends only on the velocity of the ball. c) The net work depends only on the radius of the circle. d) The net work is equal to zero joules. e) The net work is greater than zero joules.

25. 6.5.1. Which one of the following statements concerning the principle of the conservation of mechanical energy is true? a) Mechanical energy is always conserved in situations where the kinetic energy is constant. b) Mechanical energy is always conserved in situations where the gravitational potential energy is constant. c) Mechanical energy is always conserved in situations where external non-conservative forces do no work. d) Mechanical energy is always conserved in situations where external conservative forces do no work. e) Mechanical energy is always conserved in situations where the gravitational potential energy is zero joules.

26. 6.5.2. Complete the following statement: In an isolated system, the total mechanical energy remains constant if a) all exerted forces are conservative. b) all exerted forces are nonconservative. c) the work done by nonconservative forces is positive. d) the work done by nonconservative forces is negative. e) an object returns to its starting position.

27. 6.5.3. Complete the following statement: The total mechanical energy of a system remains unchanged if a) the external forces acting on the system are nonconservative. b) the external forces acting on the system are conservative. c) the kinetic energy is constant. d) the potential energy is constant. e) there are no external forces acting on the system.

28. 6.5.4. A ball is thrown vertically upward in the air. Which one of the following quantities is necessarily equal to zero at the highest point of the ball’s trajectory? a) acceleration b) net force c) potential energy d) kinetic energy e) total mechanical energy

29. 6.6.1. Complete the following statement: In situations involving non-conservative external forces, the work done by these forces a) is always negative. b) is always equal to zero. c) is always positive. d) can be either positive or negative. e) usually cannot be determined.

30. 6.7.1. Power may be expressed using all of the following units except: a) watt b) joules/second c) N  m  s d) erg/s e) ft  lb / h

31. 6.7.2. The power due to a force depends on which of the following parameters? a) the magnitude of the force and the displacement of the object b) the magnitude of the force and the velocity of the object c) the mass of the object and the velocity of the object d) the work done on the object and its displacement e) the mass of the object and the displacement of the object

32. 6.8.1. Which one of the following statements concerning the principle of conservation of energy is false? a) The total energy in the universe has a constant value. b) Kinetic energy may be converted into gravitational potential energy and heat. c) Thermal energy may be converted into kinetic energy and kinetic energy may be converted into thermal energy. d) Chemical energy may be converted into thermal energy and gravitational potential energy. e) The net work done on an object must be zero joules since energy is neither created nor destroyed in the process.