1
4. In which of the following scenarios is work done?
c. A car decelerates while traveling on a flat stretch of road.
2. A force does work on an object if a component of the force
b. is parallel to the displacement of the object.
12. Which form of energy is involved in weighing fruit on a spring scale?
d. elastic potential energy
8. Which of the following energy forms is associated with an object due to its position?
a. potential energy
13. What are the units for a spring constant?
d. N/m
1. In which of the following sentences is work used in the scientific sense of the word?
c. Sam and Rachel pushed hard, but they could do no work on the car.
19. Which of the following is the rate at which energy is transferred?
d. power
16. Which of the following is a true statement about the conservation of energy?
d. Total energy is always conserved.
21. A more powerful motor can do
b. the same work in a shorter time interval.
5. A worker does 25 J of work lifting a bucket, then sets the bucket back down in the same place. What is the total net work done on the bucket?
b. 0 J
3. If the sign of work is negative,
b. the displacement is in the direction opposite the force
14. If the displacement of a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of
d. 4
17. Why doesn’t the principle of mechanical energy conservation hold in situations when frictional forces are present?
a. Kinetic energy is not completely converted to a form of potential energy.
9. Ball A has triple the mass and speed of ball B. What is the ratio of the kinetic energy of ball A to ball B.
d. 27
11. If friction is the only force acting on an object during a given physical process, which of the following assumptions can be made in regard to the object’s kinetic energy?
a. The kinetic energy decreases.
18. A 3.00 kg toy falls from a height of 1.00 m. What will the kinetic energy of the toy be just before the toy hits the ground? (Assume no air resistance and that g = 9.81 m/s2 .)
c. 29.4 J
15. How much elastic potential energy is stored in a bungee cord with a spring constant of 10.0 N/m when the cord is stretched 2.00 m?
b. 20.0 J
6. A construction worker pushes a wheelbarrow 5.0 m with a horizontal force of 50.0 N. How much work is done by the worker on the wheelbarrow?
c. 250 J
10. What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s?
c. 108 J
7. A child pulls a balloon for 12 m with a force of 1.0 N at an angle 60 below horizontal. How much work does the child do on the balloon?
c. 6.0 J
23. A skier with a mass of 84 kg hits a ramp of snow at 32 m/s and becomes airborne. At the highest point of flight, the skier is 4.7 m above the ground. What is the skier’s gravitational potential energy at this point?
3.9 x 10^3 J
24. A scale contains a spring with a spring constant of 288 N/m. Placing a mass on the scale causes the spring to be compressed by 2.89 cm. Calculate the elastic potential energy stored in the spring.
0.120 J
25. A pole vaulter clears 6.41 m. With what velocity does the vaulter strike the mat in the landing area? (Assume no air resistance and that g = 9.81 m/s2 .)
11.2 m/s
22. A worker pushes a box with a horizontal force of 40.0 N over a level distance of 4.0 m. If a frictional force of 27 N acts on the box in a direction opposite to that of the worker, what net work is done on the box?
52 J
26. A pendulum with a mass of 4.0 kg is released from a height of 2.9 cm above the height of its resting position. How fast will the pendulum be moving when it passes through the lowest point of its swing?
0.75 m/s