1

PART 1 Work, Power, and Simple Machines Practice Test Multiple Choice Section 1.

There are _____ types of simple machines. (1.) three (2.) six (2.) eight (4.) ten

2.

The use of a force to move an object some distance is called (1.) mass (2.) work (3.) power (4.) time

3.

In a perfectly efficient machine, the work input _________ work output. (1.) is equal to (2.) is greater than (3.) is less than (4.) is independent of

4.

The _____ of a machine is the number of times it multiplies the effort force. (1.) efficiency (2.) power (3.) mechanical advantage (4.) resistance

5.

An inclined plane in spiral rotation is called a(n) (1.) wedge (2.) screw (3.) lever (4.) pulley

6.

If it takes 500 Joules to move an object in 10 seconds, what is the power output? (1.) 50 N. (2.) 5,000 N. (3.) 5,000 W. (4.) 50 W.

7.

The basic metric system unit of power is the

8.

What do we call the rate at which work is done? (1.) Efficiency (3.) Work output (4.) Power

(1.) Joule (2.) Newton (3.) Meter (4.) Watt (2.) Work input

9. Which is false about simple machines? (1.) Machines increase the amount of work which is done. (2.) Machines may multiply force. (3.) Machines may increase the rate at which work is done. (4.) Machines can change the direction of a force to suit human convenience. 10. If a person weighing 400 N. takes 6 seconds to walk up a staircase that is 3 meters high, what is his power output? (1.) 200 W. (2.) 1,200 W. (3.) 6,000 W. (4.) 7,200 W. 11. In using machines, work output is always _______ work input. (1.) greater than (2.) less than (3.) the same as (4.) unrelated to 12. The fixed point of a lever is called the (1.) effort arm (2.) fulcrum (3.) resistance arm 13. A wheel and axle is a(n) _______ machine. (1.) ideal (3.) simple (4.) automotive

(2.) compound

14. The screw is a type of (1.) wedge (2.) inclined plane (3.) gear (4.) lever 15. Which of these does not represent work done on a rock in the scientific sense? (1.) lifting a rock (2.) throwing a rock (3.) holding a rock (4.) dropping a rock 16. For work to be done, _____ must be exerted through a distance. (1.) mass (2.) specific heat (3.) potential energy (4.) a force 17. In which of these situations is NO work done? (1.) holding a box two feet off the floor (2.) carrying a box across the room (3.) pushing a box across the floor (4.) carrying a box upstairs 18. The amount of work done on an object can be increased by (1.) increasing the speed with which the object moves. (2.) decreasing the speed with which the object moves. (3.) increasing the distance the object moves. (4.) decreasing the distance the object moves.

2 19. Which of the following is NOT true about machines? (1.) They can reduce the amount of work that must be done. (2.) They can change the amount of force required. (3.) They can change the distance over which a force is exerted. (4.) They can change the direction in which a force is exerted. 20. Mechanical advantage can be increased by (1.) increasing input force. (2.) increasing output force. (3.) increasing both output and input force. (4.) decreasing both output and input force. 21. A machine with 100% efficiency has no (1.) input force. (2.) output force. (3.) mechanical advantage. (4.) friction. 22. The pivot point of a lever is called a(n) (1.) wedge. (2.) gear. (3.) fulcrum. (4.) simple machine. 23. A pair of scissors is an example of a(n) (1.) inclined plane. (2.) lever. (3.) wedge. (4.) wheel and axle. 24. A wedge is made up of a(n) (1.) inclined plane. (2.) lever. (3.) pulley. (4.) wheel and axle. True-False Section 1. Compound machines are combinations of one or more simple machines. 2. A wheel and axle is really a lever that rotates in a circle. 3. A screw is a flat slanted surface with no moving parts. 4. A wedge is an inclined planes that moves. 5. Work input is the amount of work done by the machine 6. Mechanical advantage is the numerical value that indicates how many times a machine will multiply the user's effort force. 7. Acceleration is using an unbalanced force to move an object over a distance. 8. A screw is an inclined plane in spiral rotation. 9. A pulley is a grooved wheel with a rope. Short Answer Questions

3

1. Identify the lever class in each of the diagrams at the right AND explain why you identified each as that lever class.

2.

List the six major types of simple machines.

3.

Explain how a simple machine differs from a compound machine.

4.

Show all the given information, formulae, and work to the following problems.

A box is pushed across a surface using a force of 50 Newtons to slide the box 4 meters in 10 seconds. (a.) What is the work that is done to move this box? (b.) How much power is exerted moving this box?

PART 1 Practice Test Answers Multiple Choice Section 1. 2 7. 4

2. 2 8. 4

3. 1 9. 1

4. 3 10. 1

5. 2 11. 2

6. 4 12. 2

4 13. 3 19. 1

14. 2 20. 2

15. 3 21. 4

16. 4 22. 3

17. 1 23. 2

18. 3 24. 1

True/False Section 1. true 4. true 7. false

2. true 5. false 8. true

3. false 6. true 9. true

Short Answer/Problems 1. Going from top to bottom in the picture. The first picture is a first class lever. It can be identified as suchas it has the fulcrum between the load and the effort. The second picture is a second class lever which hasthe fulcrum at the end and the load in the middle between the fulcrum and the effort. The lowest picture isthat of a third class lever which has the fulcrum at the end and the effort in the middle between the fulcrum and the load. 2. lever, wheel and axle, pulley, inclined plane, wedge, screw 3. A compound machine consists of two or more simple machines. 4. (a.) F = 50 N d = 4 m. W = Fd (b.) F = 50 N d = 4 m t = 10 s.

W = 50 N * 4 m = 200 N-m or 200 J. P=?

P = Fd t P = 50 N * 4 m 10 s P = 20 N-m = 20 W. (20 Watts) s

Chapter 4 Practice Test Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. ____ 1.Which of the following is NOT considered a simple machine? a. Wheel and axle b. Electric motor c. Lever d. Block and tackle ____ 2.A simple machine has an input force of 10 newtons and an output force of 100 newtons. What is the mechanical advantage of the simple machine? a. 0.1

5

b. 1 c. 10 d. 90 ____ 3.A block and tackle system has an input force of 2.5 newtons and an output force of 10 newtons. What is the mechanical advantage of the system? a. 0.25 b. 4 c. 7.5 d. 25 ____ 4.If the output force of a lever is located between the fulcrum and input force, the lever is a: a. first class lever. b. second class lever. c. third class lever. d. Not enough information is given. ____ 5.Which of the following levers has the largest mechanical advantage?

a. b. c. d.

Lever A Lever B Lever C All three levers have the same mechanical advantage.

____ 6.The lever in the picture will:

a. b. c. d.

stay balanced. rotate clockwise. rotate counter-clockwise. do none of the above.

____ 7.A lever has an input arm 50 centimeters long and an output arm 40 centimeters long. What is the mechanical advantage of the lever? a. 0.8 b. 1

6

c. 1.25 d. 2.0 ____ 8.The efficiency of a machine is usually expressed in: a. joules. b. watts. c. newton-meters. d. percent. ____ 9.Your friend claims to have invented a perpetual motion machine with an efficiency of 110 percent. You tell him his invention is impossible because it violates: a. Newton's first law of motion. b. Newton's second law of motion. c. Newton's third law of motion. d. the law of conservation of energy. ____10. An electric food processor uses 250 joules of electrical energy every second. Due to friction and other causes, the energy available to spin the blades to cut food is reduced to 200 joules per second. The efficiency of the food processor is: a. 25 percent. b. 50 percent. c. 80 percent. d. 125 percent. ____11. How much power is necessary to do 50 joules of work in 5 seconds? a. 5 watts b. 10 watts c. 50 watts d. 250 watts ____12. A gallon of gasoline contains chemical energy. If you pour a gallon of gasoline into your car, you could drive for about 20 miles on the highway (about 20 minutes). You could choose instead to run a lawn mower for an hour with one gallon of gasoline. If the gasoline were to come in contact with a fire, the entire gallon would burn in less than a minute. Which reaction has the most power? a. Burning the gasoline in the car b. Burning the gasoline in a fire c. Burning the gasoline in the lawn mower d. They are equal because the gasoline has the same chemical potential

7

energy in each case. ____13. The efficiency of most machines is less than 100 percent. Due to friction, energy seems to be lost. While the energy is not truly lost, it does work that is not useful or is converted to: a. thermal energy. b. chemical energy. c. potential energy. d. nuclear energy.

____14. A system of pulleys is used to lift an elevator carrying a 3,300-newton load. Assuming the pulley system is nearly friction-free, approximately how far would 10,000 joules of energy lift the elevator?

a. b. c. d.

0.3 meters 3 meters 30 meters 300 meters

Part II Chapter 4 Practice Test Answer Section MULTIPLE CHOICE 1.B 2.C 3.B 4.B 5.A 6.B 7.C

8

8.D 9.D 10.C 11.B 12.B 13.A 14.B 15.C 16.D 17.B 18.C 19.B

Part III: PRACTICE TEST QUESTIONS 38. A car changing speed from 10 mph to 40 mph would be an example of: a. Acceleration b. Constant speed c. Deceleration d. Velocity

9

40. How far had the family traveled before lunch (between points B and C)? 41. What was the average speed for the first two hours? 42. How far did the family travel between the second and third hours? 43. What was the average speed three hours into the trip? 44. What was the average speed for the entire trip? 45. A simple machine is used to lift a weight. What happens to the amount of work that must be done compared to doing the work without a machine? a. It increases b. It decreases c. It stays the same d. It depends on which simple machine is used

46. What amount of work is done when a 5 newton object is moved a distance of 10 meters? a. 1/2 joules b. 2 joules c. 5 joules

10 d. 25 joules e. 50 joules

47. Which simple machines are found in the scissors? a. b. c. d.

Inclined plane, lever Lever, pulley Pulley, inclined plane Wheel, lever

48. Why are these scissors an example of a compound machine? 49. What formula measures the work done by the scissors? a. b. c. d.

Work = force x distance Work = mass x distance Work = area x mass Work = mass x volume

The point from which most _______ 50. motion is measured . A. reference point B. the sun C. the earth D. none of these Distance traveled _______ 51. in a period of time . A. motion B. acceleration C. speed D. none of these The term normally used _______ 52. to indicate a decrease in speed

11

.

A. acceleration B. deceleration C. stop D. none of these

Acceleration toward the _______53. center of a circular path .

A. deceleration B. friction

C. negative acceleration

D. none of these

The product of the mass of an _______ 54. object and its velocity . A. acceleration B. speed C. density D. none of these Anyt hing that chan ges slid _______ 55. ing fricti on to fluid frictio n

.

A. oil B. water C. lubricant D. none of these

Which of these had the best ideas about _______56. an object moving at a constant speed .

A. Aristotle

B. Darwin

C. Newton

D. none of these

12

Forces that are opposite in _______57. direction and equal in size . A. balanced B. unbalanced C. imaginary D. none of these _______ 58. .

Force equals mass times A. momentum B. acceleration C. deceleration D. none of these

The force of a fluid that _______ 59. pushes up on an object in the fluid . A. gravity

B. buoyancy

C. free-fall

D. none of these

A force acting throu _______ 60. gh a dista nce is know as . A. work B. power C. acceleration D. none of these New tons _______ 61. are the units of . A. power B. work C. weight D. all of these

13

Machines that do _______ 62. work with one movement . A. powerful B. simple C. compound D. none of these

Modified True-False: Indicate whether the following statements are true or false. If the statement is false, correct the underlined word or phrase to make that statement true. ______ 1. The Sun is the most commonly used frame of reference that we use for motion. ______ 2. Velocity is speed in a given direction. ______ 3. Forces cause a change in motion. ______ 4. Newton proposed four laws of motion. ______ 6. Motion must occur if work is done. ______ 16. The SI prefix "milli" represents 1000. ______ 17. Mass does not change as an object is moved from one place to another. ______ 18. All objects exert a gravitational attraction on other objects. _____ 31. _____ 32.

For every action there is an equal and opposite reaction. An object in motion will stay in motion unless acted upon by another force. Short Answer Questions 1. Discuss friction as it relates to the motion of automobiles. a.) When would we want to reduce friction in a car? b.) How might we reduce friction? c.) When might we want to increase friction in a car? d.) How might we increase the friction the car makes with the road? 2. State Newton's Three Laws of Motion and discuss an example of each of these laws.

Part II TEST ANSWERS 38. a 40. 150 km 41. v= d/t V = 150 km/2 hr = 75 km/hr 42. No distance was traveled as the the graph did not change. 43. v = d/t v = 150 km/3hr. = 50 km/hr 44. v = d/t = 350 km/7 hr = 50 km/hr 45. c 46. W = Fd W = 5N (10 m) = 50 N-m = 50 J. 47. a

14 48. They are made of more than one simple machine. 49. a 50. c 51. c 52. b 53. d (centripetal acceleration) 54. d (momentum) 55. c 56. c (his first law) 57. a 58. b (Newton's second law) 59. b 60. a 61. c (or force) 62. b Modified True-False Section 1. 2. 3. 4. 5. 6.

Earth True True (unless balanced) Three 16. 1/1000 True 17. True True 18. True 31. True 32. True

Short Answer Section (Other answers may be acceptable besides those listed. Please me if you have questions.) 1.

2.

a.) b.) c.) d.)

When parts in the car that wear are rubbing together. Use a lubricant like oil or grease. On slippery roads (as they may get here as there is snow falling in NNY on 5/19/02 :-) ) Use snow tires, studded tires, or chains. (Or sand the roads!)

First Law

- states that an object at rest will remain at rest and an object in motion will remain in motion at constant velocity unless acted upon by an unbalanced force ex. a car that runs into a wall will probably stop Second Law - states that mass, force and acceleration are related in the following manner Force (N) = Mass (kg) X Acceleration (m/sec/sec) F = ma ex. it takes a larger force to move a larger mass at the same acceleration Third Law (Law of Action and Reaction) - states that for every action there is an equal and opposite reaction ex. an ice skater that pushes on a wall tends to move backward a rocket going into outer space has thrust coming out in an opposite direction of its motion

15