Chapter 10 Review

1. An 80.0-kg person carries a 25-N package up a flight of stairs. The vertical height of the stairs is 10.0 m. How much work is done?

2. A force of 1800 N is needed to keep a piano from sliding down a 10.0-m ramp. Hove much work is done?

3. A child pulls a sled through the snow with a force of 45 N applied to the rope at an angle of 30.0° with the horizontal.

a. How much work is done if they moved 15 m?
b. How much work would have been done if the rope had been pulled horizontally with the same force?

4. It takes 7500 J of work to slide a crate a distance of 15 m across a floor. A force of 650 N was applied to the rope. What angle did the rope make with the ground?

5. It took a force of 250 N to pull a crate weighing 765 N across the floor. The work done was 3500 J. How far was the crate moved?

6. A student with a mass oŁ 80.0 kg runs up three flights of stairs in 12 s. The student has gone a vertical distance of 8.0 m. What is the student's power?

7. A 9.0-kW motor lifts a 3500-kg elevator to a height of 9.5 m. How long does it take?

8. A force of 1250 N is used to push a piano up a ramp 12 m long to a height of 1.5 m above the ground The piano weighs 7500 N.

a. What is the work input?
b. What is the work output?
d. Find the ideal mechanical advantage.
a. What is the efficiency of the plane?

9. A 5.0 x 102 N load is lifted 6.0 m with a pulley. The force exerted on the pulley rope is 165 N and the efficiency is 65%. How far is the rope pulled?

B. Understanding Concepts
1. Work is done when
a. an object is at rest.           b. a force causes an object to move. c. e force is applied to an object.

2. Which of the following is a unit for work?
a. newton               b. joule   c. watt    d. joule per second

3. Which of the following is a unit for power?
a. newton-meter    b. watt    c. joule   d. newton

4. You are trying to drag the car shown below along track A For a distance of 5 m. You are pulling only along rope B with a force of 40 N. How much work do you do?
a. 50 J     b. 100 J   c. 200 J   d. 400 3

5. A crate is pushed to the top of a frictionless inclined plane 15 m long with a force of 25 N. If the crate weighs 125 N, how high is the inclined plane?
a. 0.5 m b. 1 m        c. 3 m      d. 5 m

6. A person prevents a 7500-N car with its brakes released from rolling down a hell by pushing an the car with a force of 250 N. How much work has the person done?
a. 0 J                       b. 5000 J c. 150 000 j             d. 300 000 J

7. Electric bills are paid on the basis of kilowatt-hours of electricity used. The kilowatt-hour is a unit of
a. force.  b. work.  c. Power.                d. time.

Questions 8 through 12 relate to the situation below.

A force of 25.0 N is required to push a box weighing 80.0 N up the inclined plane diagrammed

8. What is the IMA oŁ the plane? a. 1.25         b. 3          c. 3.2       d. 4

9. What is the MA of the plane? a. 1.25             b. 3          c. 3.2       d.

10. What is the input work? a. 300 J  b. 240 J   c. 80 J     d. 75 J

11. What is the output work? a. 300 J               b. 240 J  c. 80 J     d. 75 J

12. What is the efficiency of the plane? a. 40%              b. 60%    c. 80% d. 120%

If you have any questions, please email Ms. Cummings