A crate moves to the right on a horizontal surface as a woman pulls on it with a 10-N force. Rank the situations shown below according to the work done by the 10-N force, least to greatest. The displacement is the same for all cases.


2. An object moves in a circle at constant speed. The work done by the centripetal force is zero because:
A.the displacement for each revolution is zero
B.the average force for each revolution is zero
C.there is no friction
D.the magnitude of the acceleration is zero
E.the centripetal force is perpendicular to the velocity

3. A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m. An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around. The work done by the external force as the mass makes one revolution is:
A.24 J
B.47 J
C.59 J
D.94 J
E.120 J

4. A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:
A.12 J
B.15 J
C.18 J
D.20 J
E.38 J

5. When a certain rubber band is stretched a distance x, it exerts a restoring force of magnitude F = Ax, where A is a constant. The work done by a person in stretching this rubber band from x = 0 to x = L is:
B.A + 2L
C.A + 2L2

6. Which of the following bodies has the largest kinetic energy?
A.Mass 3M and speed V
B.Mass 3M and speed 2V
C.Mass 2M and speed 3V
D.Mass M and speed 4V
E.All four of the above have the same kinetic energy

7. An ideal spring is hung vertically from the ceiling. When a 2.0-kg mass hangs at rest from it the spring is extended 6.0 cm from its equilibrium length. An upward external force is then applied to the mass to compress the spring so it is 10 cm shorter than its equilibrium length. While the spring is being compressed the work done by the spring is:
A.–1.0 J
B.–0.52 J
C.–0.26 J
D.0.52 J
E.1.0 J

8. The velocity of a particle moving along the x axis changes from vi to vf. For which values of vi and vf is the total work done on the particle negative?
A.vi = 2m/s, vf = 5m/s
B.vi = –2m/s, vf = 5m/s
C.vi = –2m/s, vf = –5m/s
D.vi = 2m/s, vf = -5m/s
E.vi = –5m/s, vf = 2m/s

9. In raising an object to a given height by means of an inclined plane, as compared with raising the object vertically, there is a reduction in:
A.work required
B.distance pushed
D.force required
E.value of the acceleration due to gravity

10. A watt is:
A.kg × m/s3
B.kg × m2/s
C.kg × m2/s3
D.kg × m/s
E.kg × m2/s2

11. A kilowatt hour is a unit of:

12. A steady, 50-N force acts on a 2-kg crate that starts from rest. Two seconds after the force begins, the instantaneous power (rate of work) is:
A.75 W
B.100 W
C.1000 W
D.2500 W
E.5000 W

13. The work done by gravity during the descent of a projectile is:
D.depends for its sign on the direction of the y axis
E.depends for its sign on the direction of both the x and y axes

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