Name: 
 

ch4&5 StudyGuide


Modified True/False
Indicate whether the sentence or statement is true or false.  If false, change the identified word or phrase to make the sentence or statement true.
 

 1. 
The rate of doing work is called energy. _________________________

 

 2. 
The unit for power equal to one joule of work divided by one second of time is called a watt. _________________________

 

 3. 
The work a machine does for you is called the input work. _________________________

 

 4. 
The point around which a lever rotates is called the arm of the lever. _________________________

 

 5. 
The measure of how effective a machine is in using its energy to do work is known as the friction of the machine. _________________________

 

 6. 
A measured quantity that includes both a direction and magnitude is called a scalar quantity. _________________________

 

 7. 
The relationship between a spring’s change in length and the force it exerts is called Newton’s law. _________________________

 

 8. 
The force exerted by a table perpendicular to its surface upon a book resting on the table is called the resultant force. _________________________

 

 9. 
The force required to overcome static friction is less than the force to overcome sliding friction. _________________________

 

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 10. 
The metric unit for work is the:
A.
newton.
B.
joule.
C.
watt.
D.
meter.
 

 11. 
If forces A, B and C are equal, the work done by the forces as they are exerted on the box is:
ch4and5studyguide_files/i0130000.jpg
A.
greatest for force A.
B.
greatest for force B.
C.
greatest for force C.
D.
the same for all forces.
 

 12. 
A unit used to measure power is the:
A.
joule.
B.
newtons per second.
C.
newton-meter.
D.
watt.
 

 13. 
An automobile jack exerts a force of 4,500 newtons to raise a car 0.25 meters. The amount of work done by the jack is about ____ joules.
A.
0.00056
B.
1,100
C.
4,500
D.
18,000
 

 14. 
A 60-newton block at rest at the bottom of a frictionless incline plane is pushed up the incline:

ch4and5studyguide_files/i0160000.jpg
The amount of work done against gravity is ____ joules.
A.
0
B.
20
C.
60
D.
180
 

 15. 
The action that would require no work to be done is:
A.
holding a 100-pound object over your head.
B.
pushing a 25-kilogram box of books across the floor.
C.
pedaling a 100-newton bicycle up a small hill.
D.
lifting a balloon filled with air from the floor to a desktop.
 

 16. 
A 2.2-kilogram crate is pulled by a 30-newton force over a distance of 5 meters. The work done by pulling the crate is ____ joules.
A.
11
B.
66
C.
150
D.
330
 

 17. 
When a force applied to an object causes the object to move in the direction of the force, the object acquires:
A.
energy.
B.
mechanical advantage.
C.
efficiency.
D.
friction.
 

 18. 
Running up a flight of stairs, Maria generates 450 watts of power. If it takes her 6 seconds to go up the stairs, the amount of work she does in running up the stairs is ____ joules.
A.
0.013
B.
75
C.
450
D.
2,700
 

 19. 
Little Nellie Newton, who weighs 400 newtons, moves up a 5.0-meter climbing wall in 15 seconds. The amount of power generated by Nellie as she climbs the wall is about ____ watts.
A.
130
B.
2,000
C.
6,000
D.
30,000
 

 20. 
60 joules of work are required to lift the 10-newton object 5.0 meters as shown in the diagram:
ch4and5studyguide_files/i0220000.jpg
The amount of work done in overcoming friction as the weight is lifted is ____ joules.
A.
10
B.
50
C.
60
D.
300
 

 21. 
The diagram shows a 20-newton force being used to pull a 5-kilogram object up a hill at a constant speed:
ch4and5studyguide_files/i0230000.jpg
The amount of work done against gravity in moving the object from point A to point B is about ____ joules.
A.
100
B.
200
C.
500
D.
600
 

 22. 
Jordan lifts a 100-kilogram barbell from the floor to a height of 2.0 meters in 1.5 seconds. The amount of power he generates is about ____ watts.
A.
130
B.
200
C.
1,310
D.
1,960
 

 23. 
An electrical water heater raises the temperature of water by adding 8,000 joules of energy to the water in 40 seconds. The minimum power that must be supplied to the heater is ____ watts.
A.
0.005
B.
200
C.
3,200
D.
320,000
 

 24. 
The simple machine that operates as a ramp that curves around a shaft is a:
A.
rope and pulley system.
B.
screw.
C.
lever.
D.
gear.
 

 25. 
In a theoretical machine, work output:
A.
can be calculated by dividing output distance by output force.
B.
is always greater than the work input.
C.
can be calculated by multiplying output force by output distance.
D.
is always less than the work input.
 

 26. 
All of the following are considered to be simple machines EXCEPT:
A.
a screw.
B.
a bicycle.
C.
a jackknife.
D.
a see-saw.
 

 27. 
The force directed along the ropes of a rope and pulley system is called:
A.
thread.
B.
lead.
C.
mechanical advantage.
D.
tension.
 

 28. 
The fixed point around which levers rotate is called the:
A.
input arm.
B.
output arm.
C.
fulcrum.
D.
lever arm.
 

 29. 
Talia pulls her younger brother in a wagon 30 meters to the top of a ramp 3 meters high. If the ramp is frictionless, the mechanical advantage of this ramp is:
A.
0.10
B.
10
C.
27
D.
33
 

 30. 
The mechanical advantage of a lever is the ratio of the:
A.
length of the input arm to the length of the output arm.
B.
length of the output arm to the distance the object moves.
C.
input force to the output force.
D.
input force to the distance the object moves.
 

 31. 
If the top gear in each picture makes one complete turn, which bottom gear makes the greatest number of turns?
ch4and5studyguide_files/i0330000.jpg
A.
A
B.
B
C.
C
D.
D
 

 32. 
The diagram illustrates a rope and pulley system being used to raise a 15-newton weight:
ch4and5studyguide_files/i0340000.jpg
The tension in the rope indicated in the diagram is ____ newtons.
A.
5
B.
10
C.
15
D.
20
 

 33. 
A simple machine will sometimes multiply your:
A.
work.
B.
force.
C.
energy.
D.
All of the above
 

 34. 
If the output force of a lever is greater than the input force, the:
A.
length of the input arm is greater than the length of the output arm.
B.
mechanical advantage of the lever is less than one.
C.
mechanical advantage of the lever is equal to one.
D.
length of the output arm is greater than the length of the input arm.
 

 35. 
The diagram pictures a pulley system using 7 supporting ropes:

ch4and5studyguide_files/i0370000.jpg

If the boy in the picture weighs 140 pounds, the number of pounds of force the baby must exert to lift the boy is:
A.
70.
B.
35.
C.
20.
D.
7.
 

 36. 
The diagram shows a gear system:
ch4and5studyguide_files/i0380000.jpg
If the input gear turns 12 times, the number of turns made by the output gear is:
A.
12.
B.
18.
C.
24.
D.
48.
 

 37. 
A screw with a lead of 0.80 millimeters and a circumference of 24 millimeters is turned into a board using a screwdriver with a mechanical advantage of 4. The total theoretical mechanical advantage is:
A.
1.3
B.
3.0
C.
4.8
D.
120
 

 38. 
Josephine slides a 150-newton box 12 meters up an incline plane. If the incline plane lifts the box 4 meters as she pushes with a 60-newton force, the work input done by Josephine is ____ joules.
A.
48
B.
600
C.
720
D.
9,000
 

 39. 
The measure of how effective a machine is in using energy to do work is called:
A.
work output.
B.
transformation.
C.
mechanical advantage.
D.
efficiency.
 

 40. 
Friction is a “catch-all” term for many processes that oppose:
A.
heat.
B.
wear.
C.
motion.
D.
None of the above
 

 41. 
As fuel burns in a jet engine, it releases 40,000 joules of energy. The energy can be used to do 16,000 joules of work. The efficiency of the engine is ____ percent.
A.
20
B.
40
C.
60
D.
250
 

 42. 
The work output is 500 joules for a machine that is 25 percent efficient. The work input is ____ joules.
A.
125
B.
1,000
C.
2,000
D.
12,500
 

 43. 
An incandescent light bulb uses 60 joules of electrical energy every second. Due to heat loss, the energy available for light is reduced to only 6 joules per second. If this bulb is used to keep eggs warm in an incubator, about how efficient is the light bulb at producing heat?
A.
10 percent.
B.
20 percent.
C.
60 percent.
D.
90 percent.
 

 44. 
Luis lifts a 500-newton load in a wheelbarrow 0.15 meters by raising the handles of the wheelbarrow 0.40 meters with a 200-newton force. The amount of work used to overcome friction is ____ joules.
A.
5
B.
75
C.
80
D.
200
 

 45. 
A word meaning “size”often used to describe scalar quantities is:
A.
magma.
B.
magenta.
C.
vector.
D.
magnitude.
 

 46. 
A measured quantity that is described by stating a size and a direction is called a:
A.
scalar.
B.
magnitude.
C.
vector.
D.
victim.
 

 47. 
If a force vector acting in a northeast direction is resolved into its components, any vector acting in the north-south direction would be called a(n):
A.
hypotenuse.
B.
x-component.
C.
y-component.
D.
resultant.
 

 48. 
Vector quantities include all of the following EXCEPT:
A.
velocity.
B.
force.
C.
speed.
D.
acceleration.
 

 49. 
A scalar is a quantity that can be completely described using:
A.
direction only.
B.
magnitude only.
C.
both magnitude and direction.
D.
either magnitude or direction.
 

 50. 
Dale pulls on a wagon with 3 newtons of force toward north. Lara pulls on the wagon with 4 newtons of force toward east. The magnitude of the wagon’s resultant force is ____ newton(s).
A.
1
B.
5
C.
7
D.
25
 

 51. 
Forces in a diagram are represented by the following scale: 1 centimeter equals 5 newtons. To represent a force of 20 newtons, the length of an arrow drawn to represent the force should be ____ centimeter(s).
A.
1
B.
4
C.
5
D.
20
 

 52. 
Lily pushes a box with 50 newtons toward east. Mia pushes on the same box with 50 newtons toward south. The direction of the box’s resultant force is most clearly stated as:
A.
45º.
B.
135º.
C.
225º.
D.
315º.
 

 53. 
The diagram below represents a force acting at point P:
ch4and5studyguide_files/i0550000.jpg
The pair of forces that could represent x and y components of this force are:
A.
1
B.
2
C.
3
D.
4
 

 54. 
Maya kicks a soccer ball 2 newtons toward north. At the exact same time, Casey kicks the same ball toward west. The resultant force of the soccer ball is about 36 newtons. The force that Casey kicks the soccer ball toward west is ____ newtons.
A.
16
B.
20
C.
30
D.
56
 

 55. 
The relationship between a spring’s change in length and the force it exerts is called:
A.
Newton’s law.
B.
Hooke’s law.
C.
Archimedes’ principle.
D.
Galileo’s theory.
 

 56. 
When a spring is compressed:
A.
the potential energy stored in the spring increases.
B.
the potential energy stored in the spring decreases.
C.
the spring constant of the spring is decreased.
D.
the spring constant of the spring is increased.
 

 57. 
When the net force acting on an object is zero, this ALWAYS causes a condition of motion referred to as:
A.
rest.
B.
positive acceleration.
C.
negative acceleration.
D.
equilibrium.
 

 58. 
When you are seated in a chair, the force exerted on you by the chair is called the:
A.
normal force.
B.
gravitational force.
C.
weight.
D.
mass.
 

 59. 
A dictionary whose mass is 1.0 kilograms lying on a stationary table exerts a force of 9.8 newtons on the table. The force exerted on the dictionary by the table is ____ newtons.
A.
1.0
B.
8.8
C.
9.8
D.
10.8
 

 60. 
A car drives from east to west over a bridge supported by the ground at either end as illustrated in the diagram:
ch4and5studyguide_files/i0620000.jpg
The force exerted by the ground on the bridge at the west end is ____ tons.
A.
58
B.
39
C.
20
D.
19
 

 61. 
Eric is pedaling his bicycle due west on the Mohawk River bicycle path at a constant speed of 17 miles per hour. As he is pedaling, a 3 mile per hour wind is blowing from the east. The statement that best describes the forces acting on Eric’s bicycle is:
A.
the net force acting on the bike is zero.
B.
a greater net force is acting toward the east.
C.
a greater net force is acting toward the west.
D.
Not enough information is given to answer the question.
 

 62. 
A force of 2 newtons is required to stretch a spring 4 centimeters. The amount of force required to stretch the same spring 8 centimeters is ____ newton(s).
A.
1
B.
2
C.
4
D.
8
 

 63. 
If the stretching force on a spring is doubled, the length of the spring will be:
A.
unchanged.
B.
doubled.
C.
quadrupled.
D.
halved.
 

 64. 
A spring with a large spring constant:
A.
always stretches a large amount.
B.
never stretches a large amount.
C.
stretches a large amount with a small force.
D.
stretches a small distance with a large force.
 

 65. 
The force that resists the motion of objects or surfaces in contact with one another is called ____ force.
A.
inertial
B.
frictional
C.
normal
D.
net
 

 66. 
The force of friction between two surfaces can be reduced by all of the following EXCEPT:
A.
separating surfaces with a lubricant.
B.
changing rolling friction to sliding friction.
C.
separating surfaces with a layer of air.
D.
sanding rough surfaces smoother.
 

 67. 
Two moving surfaces are in contact with one another. The force of friction between the surfaces can be changed by all of the following methods EXCEPT:
A.
placing lubrication between the surfaces.
B.
changing the types of surfaces.
C.
changing the force used to move the surfaces.
D.
altering the force pushing the two surfaces together.
 

 68. 
To overcome static friction to start an object sliding on a level surface, a 100-newton force is used. The magnitude of the force needed to keep the object the sliding is:
A.
more than 100 newtons.
B.
equal to 100 newtons.
C.
less than 100 newtons.
D.
unknown using the given information.
 

 69. 
Of the following, the statement about friction which is NOT true is:
A.
friction is always present.
B.
friction can be useful.
C.
friction can be harmful.
D.
friction can be eliminated.
 

 70. 
As Joshua accelerates in his pickup truck at 2.0m/sec2, a 200-kilogram box in the back does not slide. The force of friction that must act on the box to keep it from slipping in the back of the truck is ____ newtons.
A.
100
B.
200
C.
400
D.
1,960
 

 71. 
The diagram below represents a box sliding down an incline:
ch4and5studyguide_files/i0730000.jpg
The force of friction acting on the box is directed toward:
A.
1
B.
2
C.
3
D.
4
 

 72. 
Pulling on a rope with a force of 100 newtons at an angle ch4and5studyguide_files/i0740000.jpg of 30 degrees, Cheung pulls a box across a surface at a constant speed:
ch4and5studyguide_files/i0740001.jpg
The magnitude of the frictional force resisting the motion is ____ newtons.
A.
100
B.
87
C.
50
D.
0
 

Completion
Complete each sentence or statement.
 

 73. 
The transfer of energy that results from applying a force over a distance is called ____________________.
 

 

 74. 
If Sam pushes a block one meter with a force of one newton, he has done one ____________________ of work on the block.
 

 

 75. 
For an object to do work, it must possess ____________________.
 

 

 76. 
If Isaac pushes on a box with a 20-newton force, no work is done if the box does not ____________________.
 

 

 77. 
The work Brandon does in lifting a rock is calculated by multiplying the weight of the rock by the change in the ____________________ of the rock.
 

 

 78. 
A device with moving parts that work together to accomplish a task is called a ____________________.
 

 

 79. 
The ratio of the output force to the input force is called _________________________ (two words).
 

 

 80. 
The pulling force that always acts along the direction of the rope in a pulley system is called ____________________.
 

 

 81. 
A fluid such as oil used to reduce friction is called a ____________________.
 

 

 82. 
The rotational equivalent of force that causes objects to rotate about a point is called ____________________.
 

 

 83. 
A see-saw that is balanced has a net torque of zero applied to it. It is said to be in _________________________ (two words).
 

 

 84. 
The size of a scalar or vector quantity may be called its ____________________.
 

 

 85. 
The sum of two or more vectors is called the ____________________.
 

 

 86. 
When the net force that acts on a body is zero, the forces are balanced. This represents a condition called ____________________.
 

 

 87. 
A diagram that uses vectors to show all of the forces acting on an object is known as a ____________________ diagram.
 

 

 88. 
A kilowatt-hour is a measure of what physical quantity?  ____________________.
 

 

Short Answer
 

 89. 
On Monday, Bik runs upstairs carrying a heavy book. The next day, she walks upstairs carrying the same book. Compare Bik’s work and power on Monday and Tuesday.
 

 90. 
List four types of simple machines.
 

 91. 
Name the three basic parts of a lever.
 

 92. 
State the relationship between the mechanical advantage of a pulley system and the number of strands supporting the pulley.
 

 93. 
Compare the output work to the input work for a machine.
 

 94. 
Name the quantity represented by each of the ratios below:

a. ____________________ ch4and5studyguide_files/i0980000.jpg

b. ____________________ ch4and5studyguide_files/i0980001.jpg

c. ____________________ ch4and5studyguide_files/i0980002.jpg
 

 95. 
List three ways to reduce friction.
 

 96. 
Identify each of the following as a scalar or vector quantity:
a. speed
b. mass
c. velocity
d. length
e. temperature
f. time
g. weight
 

Problem
 

 97. 
If one horsepower is equal to 746 watts, how much horsepower does a highly trained athlete generate by doing 350 joules of work per second for an hour?
 

 98. 
Calculate the power required to move a 2,000-kilogram automobile to the top of a 100-meter hill in 15.0 seconds. Express the power both in units of watts and horsepower.
 

 99. 
Carlos accelerates his 3-kilogram skateboard to a speed of 3.96 m/sec in 3 seconds in a distance of 4 meters. How much work does he do?
 

 100. 
Calculate the theoretical mechanical advantage of a ramp that is 2 meters high and 10 meters long.
 

 101. 
How much force would be required to lift a 350-newton weight by using a pulley system with a mechanical advantage of 5?
 

 102. 
A 70-kilogram bicycle racer climbs a 500-meter hill by doing 400,000 joules of work. Calculate the efficiency of his bicycle.
 

 103. 
Using a scale of 1 centimeter = 1 newton, represent the following displacement vectors:
(a) 5 newtons west
(b) 3 newtons, 270º
(c) 4 newtons, 0º
 

 104. 
Alexis pulls with 3 newtons on a toy doll toward east. Brianna pulls on the same toy toward south with 2 newtons. Calculate the magnitude of the resultant force on the toy.
 

 105. 
A scale of 1 centimeter = 1 newton was used to draw the vector represented. Using a centimeter ruler, draw and identify the magnitude of the horizontal and vertical components of the 4.5-newton force illustrated in the vector drawing below:
ch4and5studyguide_files/i1100000.jpg
 

 106. 
A can of soda sits motionless on a table. Make a free-body diagram of the forces acting upon the can.

ch4and5studyguide_files/i1110000.jpg
 

 107. 
When a 20-newton weight is hung on a spring, it stretches 16 centimeters. How far does the spring stretch if a 5.0-newton weight is hung from the spring?
 

Essay
 

 108. 
Explain the following statement: “Applying a force to an object does not necessarily give the object energy.”
 

 109. 
Isaiah and Ben have a race to carry identical objects from a point at the bottom of a hill to the same point at the top. Isaiah runs straight up a very steep part of the hill and finishes first. Ben chooses a more gradual ascent and, walking, arrives after Isaiah. Who has done more work? Explain your answer.
 

 110. 
Describe each type (class) of lever, and give an example of each class.
 

 111. 
Explain why the efficiency of machines is always less than 100 percent. In the discussion, use the words efficiency, work input, work output, heat, and friction.
 

 112. 
Friction can be useful, but it is often desirable to reduce the amount between surfaces. List 3 examples of useful friction and 3 examples of friction that should be reduced.
 



 
Check Your Work     Reset Help