Lesson 2.01 Work and Work-Energy Theorem
Self-Check Quiz
1. If it takes 40 J to push a large box 4 m across a floor, what is the magnitude of the force on the box? The push is in the same direction as the velocity of the box.
a. 4 N
b. 10 N
c. 40 N
d. 160 N
e. none of the above
Answer: _____
2. A 1500 kg car travels at a speed of 20 m/s. What is its kinetic energy?
a. 15.0 x 105 J
b. 2.5 x 105 J
c. 3.0 x 105 J
d. 6.0 x 105 J
Answer: _____
3. A 15.0 kg crate, initially at rest, slides down a 2.0 m long frictionless ramp inclined at an angle of 20o. What is the velocity of the crate at the bottom of the ramp? (g = 9.8 m/s2)
a. 6.1 m/s
b. 3.7 m/s
c. 10.7 m/s
d. 8.3 m/s
Answer: _____
4. A block slides down an inclined plane. Which force does zero work?
a. the weight
b. friction
c. normal force
d. all of the above
e. none of the above
Answer: _____
5. If a car moving at 15 m/s skids to a stop after 20 m, how far will it skid if it is moving at 45 m/s? Assume that the braking force is constant.
a. 20 m.
b. 50 m.
c. 90 m.
d. 120 m.
e. 180 m.
Answer: _____
6. A loaded sled weighs 5000 N. It is pulled on level snow by a horizontal force. The coefficient of kinetic friction between sled and snow is 0.05. How much work is done by the force if the sled traveled 1000 m at constant speed?
a. 2.5*104 J
b. 2.5*105 J
c. 5.0*105 J
d. 2.5*106 J
e. 5.0*106 J
Answer: _____
7. An 8000-N car is moving at 12 m/s along a horizontal road. The driver applies the breaks and the car skids to a stop. How much kinetic energy is lost?
a. 4.8*104 J
b. 5.9*104 J
c. 1.2*105 J
d. 5.8*105 J
e. 4.8*106 J
Answer: _____
8. The amount of work required to stop a truck is equal to the:
a. velocity of the truck
b. kinetic energy of the truck
c. mass of the truck times its acceleration
d. mass of the truck times its velocity
e. square of the velocity of the truck
Answer: _____
9. A 5.0-kg brick is moving horizontally at 6.0 m/s. In order to change its speed to 10.0 m/s, the net work done on the brick must be:
a. 40 J
b. 90 J
c. 160 J
d. 400 J
e. 550 J
Answer: _____
10. If the work done on a particle is zero, then:
a. the net force is zero
b. the displacement is zero
c. the acceleration is zero
d. all of the above are possible
Answer: _____
11. A crate is pulled 7.0 m across a smooth surface. The tension in the rope pulling the crate is 40 N. If the work on the crate is 247 J, what is the angle the rope makes with the horizontal?
a. 28o
b. 41o
c. 47o
d. 62o
Answer: _____
12. Which of the following 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
Answer: _____
13. A 40 N box is pulled up an inclined plane at a constant velocity. If the plane is inclined at an angle of 37o to the horizontal and the box travels 5 m, what is the work done by the force of gravity?
a. 120 J
b. 6 J
c. 1180 J
d. 200 J
Answer: _____
14. A 20.0-N weight starts from rest and slides down a 150 m long inclined plane which makes an angle of 30o with the horizontal. At the bottom of the plane, the speed of the weight is 15.0 m/s. What work is done by friction?
a. 1270 J
b. 1500 J
c. -1500 J
d. 229 J
Answer: _____