1. A force acting on a particle is conservative then:
 A. its work is zero when the particle moves exactly once around any closed path
 B. its work equals the change in the kinetic energy of the particle
 C. it obeys Newton's second law
 D. it obeys Newton's third law
 E. it is not a frictional force

2. A nonconservative force:
 A. violates Newton's second law
 B. violates Newton's third law
 C. cannot do any work
 D. must be perpendicular to the velocity of the particle on which it acts
 E. none of the above

3. A 6.0-kg block is released from rest 80 m above the ground. When it has fallen 60 m its kinetic energy is approximately:
 A. 4800 J
 B. 3500 J
 C. 1200 J
 D. 120 J
 E. 60 J

4.

A ball is held at a height H above a floor. It is then released and falls to the floor. If air resistance can be ignored, which of the five graphs below correctly gives the mechanical energy E of the Earth-ball system as a function of the altitude y of the ball? A. I
 B. II
 C. III
 D. IV
 E. V

5. A 2-kg block is thrown upward from a point 20 m above the Earth's surface. At what height above the Earth's surface will the gravitational potential energy of the Earth-block system have increased by 500 J?
 A. 5 m
 B. 25 m
 C. 46 m
 D. 70 m
 E. 270 m

6. An elevator is rising at constant speed. Consider the following statements:
I. the upward cable force is constant
II. the kinetic energy of the elevator is constant
III. the gravitational potential energy of the Earth-elevator system is constant
IV. the acceleration of the elevator is zero
V. the mechanical energy of the Earth-elevator system is constant
 A. all five are true
 B. only II and V are true
 C. only IV and V are true
 D. only I, II, and III are true
 E. only I, II, and IV are true

 7 For a block of mass m to slide without friction up the rise of height h shown, it must have a minimum initial speed of:  Answer:

8. A 0.20-kg particle moves along the x axis under the influence of a stationary object. The potential energy is given by U(x) = 8x2 + 2x4, where U is in joules and x is in meters. If the particle has a speed of 5.0 m/s when it is at x = 1.0 m, its speed when it is at the origin is:
 A. 0
 B. 2.5 m/s
 C. 5.7 m/s
 D. 7.9 m/s
 E. 11 m/s

9.

Which of the five graphs correctly shows the potential energy of a spring as a function of its elongation x? A. I
 B. II
 C. III
 D. IV
 E. V

10. A force of 10 N holds an ideal spring with a 20-N/m spring constant in compression. The potential energy stored in the spring is:
 A. 0.5 J
 B. 2.5 J
 C. 5 J
 D. 10 J
 E. 200 J

11. A 700-N man jumps out of a window into a fire net 10 m below. The net stretches 2 m before bringing the man to rest and tossing him back into the air. The maximum potential energy of the net is:
 A. 300 J
 B. 710 J
 C. 850 J
 D. 7000 J
 E. 8400 J

12. Given a potential energy function U(x), the corresponding force ¢ is in the positive x direction if:
 A. U is positive
 B. U is negative
 C. U is an increasing function of x
 D. U is a decreasing function of x
 E. it is impossible to obtain the direction of ¢ from U

13.

As a particle moves along the x axis it is acted by a conservative force. The potential energy is shown below as a function of the coordinate x of the particle. Rank the labeled regions according to the magnitude of the force, least to greatest. A. AB, BC, CD
 B. AB, CD, BC
 C. BC, CD, AB
 D. BC, AB, CD
 E. CD, BC, AB

14.

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of stable equilibrium are: A. only a
 B. only b
 C. only c
 D. only d
 E. b and d

15. The potential energy of a body of mass m is given by U = –mgx + 1/2kx2. The corresponding force is:
 A. –mgx2/2 + kx3/6
 B. mgx2/2 – kx3/6
 C. –mg + kx/2
 D. –mg + kx
 E. mg – kx This is the end of the test. When you have completed all the questions and reviewed your answers, press the button below to grade the test.