SCIENCE | LEVEL 8
Student Edition Sample Page
Name __________________________________________
Unit 7 Introduction
Readiness Standard 8.6(A)
Motivation Station: Scientific Fact
Forces cause destruction when they become unbalanced.
Earthquakes cause changes in speed and direction of tectonic
plates when forces in one direction overpower the opposing
forces. The unbalanced force causes property damage and
sometimes loss of life.
After this lesson I will be able to:
• Demonstrate and calculate how unbalanced forces change the speed or direction of an object’s motion.
Comparative and Experimental Investigations
Activity 1: Demonstrating Unbalanced Forces
An unbalanced force is a push or pull that causes an object to move, stop, or change direction. Unbalanced
forces cause many phenomena in the world around us.
Demonstrate unbalanced forces in the situations below. Diagram and label the unbalanced force with varying
sizes of arrows and describe the result of the unbalanced force in terms of speed and change of direction.
Situation
Diagram
Result of Unbalanced Force
Tug-of-war
Chair
moving
Ball
moving
Toy truck
moving
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Unit 7 Introduction
Readiness Standard 8.6(A)
Activity 2: Measuring Unbalanced Forces
Number of Washers
Use a spring scale to measure the unbalanced force required to move washers from rest. During each trial,
make sure the washers are moved at least 25 cm to the right with the same force. Record the force values in
the table and record a relative speed (slow, fast, very fast) for each trial.
Trial
Number of Washers
1
6
2
8
3
10
Force (N)
Relative Speed
Was speed affected by the number of washers being pulled by the unbalanced force? Explain your answer.
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Type of Surface
Different surfaces can affect the unbalanced force required to move the washers from rest and the speed at
which the washers move. Measure the unbalanced force required to move ten washers at least 25 cm with the
same force. Record a force value and a relative speed for each trial.
Trial
Number of Washers
Surface
1
10
Carpet
2
10
Concrete
3
10
Sandpaper
4
10
Smooth surface
Force (N)
Relative Speed
How does surface type affect the amount of unbalanced force required to move washers from rest?
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Friction
Friction interferes with an object’s ability to move freely on a surface. The force of friction opposes movement.
A smooth surface provides the least amount of friction. It will be assumed that the force of friction is almost
zero on a smooth surface. Calculate the force of friction for each surface.
Force of Friction = Force of Smooth Surface – Force of Other Surface
Trial
Surface
Force of Friction (N)
Force of Smooth Surface (N)
1
Carpet
0
2
Concrete
0
3
Sandpaper
0
Force of Surface (N)
Draw a diagram that shows the unbalanced force and friction as they affect the movement of the washers. Use
arrows to represent the size and direction of the forces.
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Unit 7 Guided Practice
Readiness Standard 8.6(A)
1
2
According to the first law of motion, an object
remains in motion or at rest until an unbalanced
force acts upon it. Who played the most
important role in discovering that unbalanced
forces change the motion of an object? 8.3(D)
A
Albert Einstein
C
Sir Isaac Newton
B
Gregor Mendel
D
Watson and Crick
4
Which of the following conclusions is based on
the data in the table? 8.2(E)
Balanced
F
H
G
J
Unbalanced
5
5N
Which illustration shows an unbalanced force
causing a change in motion?
5N
5N
75 N
A surfer is waiting for a wave. A wave comes and
pushes the surfer towards the shore.
5N
75 N
75 N
75 N
25 N
25 N
Which statement best describes the motion
of the surfer?
75 N
25 N
A
The surfer travels to the left. The speed
increases due to net force of 105 N.
B
The surfer travels to the right. The speed
increases due to net force of 105 N.
C
The surfer travels to the left. The speed is
constant due to net force of 105 N.
D
The surfer travels to the right. The speed is
constant due to net force of 105 N.
75 N
F
There is no pattern between balanced and
unbalanced forces.
G
Balanced forces are equal and opposite in
direction, while unbalanced forces are different
sizes in the same or opposite directions.
H
Forces are always equal and opposite
in direction for both balanced and
unbalanced forces.
J
3
6
Balanced forces are different sizes in the
same or opposite direction, while unbalanced
forces are equal and opposite in direction.
Which example does NOT exhibit unbalanced
forces?
A
5 N and
5N
B
5 N and
10 N
C
10 N and
10 N
D
10 N and
10 N
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100 N
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A car runs out of gas at a red light, and someone
begins to push the car forward with 10 N of force.
The force of friction is 3 N. What happens to the
speed and direction of the car?
F
The car will move forward with a force of
10 N with a constant speed.
G
The car will move forward with a force of
7 N with an increasing speed.
H
The car will move backward with a force of
10 N with an increasing speed.
J
The car will move backward with a force of
7 N with a constant speed.
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Unit 7 Check for Understanding
Readiness Standard 8.6(A)
1 A pinball machine requires a player to move
flippers in order to move a ball. The flipper hits
the ball with a force of 100 N.
4
According to the picture, what will happen to the
motion of the toy truck?
25 N
If the pinball machine has a frictionless surface,
what would be the force on the ball? Record and
bubble your answer in the box below.
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
3
3
3
3
3
3
4
4
4
4
4
4
5
5
5
5
5
5
6
6
6
6
6
6
7
7
7
7
7
7
8
8
8
8
8
8
9
9
9
9
9
9
5
9N
F
The toy truck will stay in place.
G
The toy truck will move left with a force
of 16 N.
H
The toy truck will move right with a force
of 4 N.
J
The toy truck will move right with a force
of 16 N.
How can the box increase its speed to the right?
F = 30 N
Box
v = 1.5 m/s
20.0 kg
Smooth surface
2
An object rests on a desk. A student walks by
and bumps the desk, and the object begins to
move. What causes the object to move?
A
Add a force to the left
B
Place the box on a rough surface
F
The additional force the student applies to
the desk causes an unbalanced force.
C
Add a force to the right
G
The additional force the student applies to
the desk causes the force to stay balanced.
D
Add a force above the box
H
The object begins to move because no
additional force is applied.
J
The object stops moving because additional
force is applied.
6
Object X is at rest until unbalanced forces are
applied. Object X will —
5.4 N
3
76
Which example does NOT demonstrate an
unbalanced force causing a change in speed
or direction of an object’s motion?
X
21 N
F
move right at a constant speed
A
Kicking a soccer ball
G
move right at an increasing speed
B
Picking up a box from the floor
H
move left at an increasing speed
C
Pushing a grocery cart
J
Not here
D
Relaxing in a recliner
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Unit 7 Check for Understanding
Readiness Standard 8.6(A)
Scientific Investigation and Reasoning Skills: Questions 7–14
7
A student uses a spring scale to test the results
of different amounts of push and pull forces on a
block of wood and draws the following diagram in
a science journal.
9
A
42
15
block of wood
What unit should be used to label the
measurement at point A? 8.2(C)
A
Meters
B
Newtons
C
Kilograms
D
Amperes
10
8
A student builds a toy car propelled by air from an
untied balloon. The balloon is filled with different
amounts of air, and the car is released on a hard,
smooth surface. Results are recorded below.
A student wants to know how much force it will
take to send a paper airplane from one side of
the science lab to the other. What would be the
best way to answer this question? 8.2(B)
A
Build several airplanes with different
wingspans. Make a chart that shows each
plane’s wingspan and distance traveled.
B
Build several airplanes with different kinds of
paper. Record the type of paper and distance
traveled for each flight.
C
Allow the three strongest students to throw
the same airplane. Chart the results.
D
Use different amounts of force to fly the
same airplane. Record the amount of force
and distance for each flight.
What is one advantage of using arrows to
represent forces applied to an object? 8.3(C)
Trial
Force (N)
Distance (m)
Time (s)
1
2.4
2.0
12
2
2.7
2.5
13
3
3.5
3.2
13
F
The forces are easy to see.
4
5.1
5.1
14
G
The different sizes of the arrows make it
easy to determine which force is greater.
H
The different sizes of the arrows make it
difficult to determine which force is greater.
J
There is no label, so force values cannot
be determined.
Based on the information provided in the table,
when force changes, what other value changes
for the toy car? 8.2(E)
F
Mass
G
Weight
H
Speed
J
Friction
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Unit 7 Check for Understanding
11
Readiness Standard 8.6(A)
A group of students designs a comparative
investigation to test forces at points A and B on
a brick moving across a table. When the brick is
pulled at point A, it moves to the left. When the
brick is pulled at point B, it moves to the right.
A
13
B
Brick moves left
A
A group of students applies different amounts of
force to toy vehicles while investigating changes
in the speed of the toy. Which piece of equipment
would measure the force applied to the toy
vehicle in each trial? 8.4(A)
A
Psychrometer
B
Spring scale
C
Balance
D
Spectroscope
B
Brick moves right
The forces applied are shown to be —
A
balanced
B
equal
C
unbalanced
D
less than zero
8.2(B)
14
Forces are acting on a box in all four directions.
15 N downward
17 N to
the right
18 N upward
12 Two students demonstrate unbalanced forces by
pulling in opposite directions on a rope. Which lab
safety equipment, in addition to safety goggles,
would best protect the students during this
demonstration? 8.4(B)
78
F
Gloves
G
Lab apron
H
Fume hood
J
None of the above
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23 N to
the left
Which direction will the box move?
™
F
Down and to the right
G
Down and to the left
H
Up and to the right
J
Up and to the left
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Name __________________________________________
Unit 7 Critical Thinking
Readiness Standard 8.6(A)
Thrill Ride
nthesis
Sy
Design a new thrill ride to be built at a local theme park. The ride will showcase creative
ways to use unbalanced forces to change the speed and direction of a rider’s motion. Create
a schematic drawing that shows the ride’s pathway. Label each area of unbalanced force and
the intended result of the change in forces.
C re a t e
Explain how this amusement park ride demonstrates the use of unbalanced forces.
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_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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Unit 7 Formative Assessment/Journal
Readiness Standard 8.6(A)
Formative Assessment
A marble is rolled in a straight line inside a box. Indicate the size and direction of an unbalanced force
necessary to change the speed and/or direction of the marble’s motion.
2N
Provide evidence to support why your unbalanced force will cause this change in speed and/or direction for the
marble.
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
Science Journal
Write a narrative about a beneficial experience in which unbalanced forces resulted in a change in speed or
direction.
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
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Student Edition Sample Page
Name __________________________________________
Unit 7 Vocabulary Activity
Readiness Standard 8.6(A)
Science Vocabulary Builder
Explain the term unbalanced forces by completing the following graphic organizer.
Definition
Illustration
Related words
Examples
Non-examples
Unbalanced
Forces
Sentence
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Unit 7 Homework
Readiness Standard 8.6(A)
Unbalanced Forces at Home
Investigate unbalanced forces at home. Give three examples of unbalanced forces and illustrate them in the
space provided.
Unbalanced Forces
1.
2.
3.
How are all unbalanced forces alike? Explain your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Parent Activities
1. Help your student determine three examples of unbalanced forces at home.
2.Researchunbalancedforcesanddeterminehowtheresultscanbenefitorharm
an object or person.
3. Discuss the importance of unbalanced forces in everyday life.
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Getting Started
Reporting Category 2
The student will demonstrate an understanding of force, motion, and energy and their relationships.
TEKS
The student knows that there is a relationship between force, motion, and energy.
8.6(A) Readiness Standard
Demonstrate and calculate how unbalanced forces change the speed or direction of an object’s motion.
Unpacking the Standard
In order to master this standard, students must be able to show how unbalanced forces change the
speed and/or direction of an object’s motion, as well as the magnitude of the force causing the changes
at the comprehension and application levels of Bloom’s Taxonomy.
Prerequisite Standards
Prior to 8th Grade, students studied these science concepts which laid the foundation for understanding
8.6(A).
Grade
Level
K
TEKS
Description
Observe and describe the location of an object in relation to another such as above, below, behind, in front
K.6(C)
of, and beside.
K.6(D)
Observe and describe the ways that objects can move such as in a straight line, zigzag, up and down, back
and forth, round and round, and fast and slow.
1.6(C) Describe the change in the location of an object such as closer to, nearer to, and farther from.
1
1.6(D)
Demonstrate and record the ways that objects can move such as in a straight line, zig zag, up and down,
back and forth, round and round, and fast and slow.
2
2.6(C)
Trace the changes in the position of an object over time such as a cup rolling on the floor and a car rolling
down a ramp.
3
3.6(C) Observe forces such as magnetism and gravity acting on objects.
4
4.6(D)
5
5.6(D) Design an experiment that tests the effect of force on an object.
6
6.8(B)
Identify and describe the changes in position, direction, and speed of an object when acted upon by
unbalanced forces.
7
7.7(C)
Demonstrate and illustrate forces that affect motion in everyday life such as emergence of seedlings,
turgor pressure, and geotropism.
Design an experiment to test the effect of force on an object such as a push or a pull, gravity, friction, or
magnetism.
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Science Teacher Express
Teacher Instructions
Use this information to build your background knowledge or review content.
Unbalanced Forces
• Unbalanced forces can cause an object to speed up, slow down, change from rest to motion,
change from motion to rest, or change the direction in which the motion occurs.
• An object will remain at rest or in constant motion unless unbalanced forces act on the object.
• Types of forces include gravity, friction, and magnetism.
• Gravity is a force that pulls objects toward each other and is the force that pulls towards the
center of Earth.
• Friction exists when two surfaces rub against each other.
• The force of friction opposes movement.
• Magnetism is the pulling force of a magnet. The magnetic force is the push or pull away or
towards a magnet.
• Forces are measured in newtons (N) with the International System of Units (SI).
• A spring scale is a tool that measures force.
balanced
forces
250 N
250 N
truck stays at rest
larger
force
unbalanced
forces
smaller
force
250 N
125 N
truck moves in this direction
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Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Vocabulary Focus
Teacher Instructions
Use the vocabulary builder in the student edition and the vocabulary activity to review and practice the
unit vocabulary terms.
The following are essential vocabulary terms for this unit.
balanced forces in motion
demonstrate
motion
calculate
direction
speed
change
force
unbalanced force
Vocabulary Activity
Introduce the new vocabulary term and display the vocabulary term. Discuss the term with the students.
Have each student write the term in his/her vocabulary journal. Ask students to define the term and use
the term in a sentence. Have students work in small groups to create a story using the vocabulary term
or a group of vocabulary terms. Then have students share the story with the class.
Suggested Formative Vocabulary Assessment
Present students with an analogy prompt:
A balanced force is like _______________ because _______________________________.
An unbalanced force is like _______________ because _______________________________.
Enrichment Connections
Enrichment Literature
Force & Motion – Peter Lafferty
Forces and Motion – Casey Rand
Forces and Motion – Nevin Katz
Uncovering Student Ideas in Physical Science: 45 NEW Force and Motion Assessment Probes – Page Keeley and
Rand Harrington
Science Websites
Forces Lab: http://www.pbs.org/wgbh/buildingbig/lab/forces.html
Forces in 1 Dimension: http://phet.colorado.edu/en/simulation/forces-1d
Parkworld Plot: http://www.engineeringinteract.org/resources/parkworldplot.htm
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Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Introduction
(student pages 73–74)
Materials
Teacher Instructions
Activities 1 and 2 can be conducted in groups or in stations. Evaluate student
understanding throughout the activities as a formative assessment of
learning.
Activity 1: Demonstrating Unbalanced Forces
Students will diagram the unbalanced forces applied to each situation and
discuss the results of the unbalanced forces on the motion of the object.
Tug-of-War Station
Provide students with a rope for tug of war. Have two students pull on
opposite ends of the rope with varying amounts of force applied in each
direction. Have students discuss the effects of the unbalanced forces. Label
the tug-of-war diagram and explain the results of the unbalanced forces.
Chair-Moving Station
Provide students with a chair and instruct one student to move the chair
with varying amounts of force. Have students discuss the effects of the
unbalanced forces. Label the chair-moving diagram and explain the results of
the unbalanced forces.
Ball-Moving Station
Provide students with a ball and instruct one student to move the ball
with varying amounts of force. Have students discuss the effects of the
unbalanced forces. Label the ball-moving diagram and explain the results of
the unbalanced forces.
Activity 1: Per Group/Station
•
•
•
•
•
•
student editions
rope for tug-of-war
chair
ball
toy truck
safety goggles
Activity 2: Per Group/Station
•
•
•
•
•
•
•
•
•
•
student editions
spring scale
10 washers
string
sandpaper
carpet (access)
concrete (access)
smooth surface (access)
metric ruler
safety goggles
Toy Truck-Moving Station
Provide students with a toy truck. Instruct one or two students to move
the toy truck with varying amounts of force. Have students discuss the effects of the unbalanced forces. Label the toy
truck-moving diagram and explain the results of the unbalanced forces.
Activity 2: Measuring Unbalanced Forces
1. Provide each group a spring scale, ten washers, string, sandpaper, and access to carpet, concrete, and a smooth surface.
2. Have students tie together with string the appropriate number of washers for each trial and hook the spring scale to the
other end of the string.
3. Tell students to pull six washers to the right across a surface for at least 25 cm with the same amount of force. Record the
force value and relative speed of the washers in the table provided in the student editions. Repeat procedure.
4. Instruct students to pull ten washers across a carpeted surface for at least 25 cm with the same amount of force. Record
the force value and relative speed of the washers in the table provided in the student editions.
5. Repeat procedure for concrete, sandpaper, and a smooth surface, recording all data in the table provided in
the student editions.
6. Have students calculate the force of friction values for each surface in relation to the smooth surface.
7. Complete the discussion questions in the student edition.
8. Discuss results recorded by the students.
Questions to Guide Inquiry
1.
2.
3.
4.
5.
6.
7.
110
What are unbalanced forces? What are examples of unbalanced forces?
How do unbalanced forces affect objects?
How can unbalanced forces be produced?
How are balanced forces different from unbalanced forces?
What variables were manipulated during the investigations?
How can speed and direction change due to unbalanced forces?
Which surface has the greatest force from friction? How does friction affect the speed of the washers?
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Guided Practice Strategies
(student page 75)
Teacher Instructions
As a class or in small groups, read through each question together and discuss the correct and
incorrect responses, revealing common understandings and misconceptions. Model strategies to help
students logically think about each answer choice. Assess student understanding as the questions and
answers are discussed.
Question 1
Who played the most important role in discovering that unbalanced forces change the
motion of an object?
• Did Albert Einstein’s work involve balanced and unbalanced forces?
No, Albert Einstein worked in the field of physics, but most of his work pertained to the study of
quantum theory. Answer A is incorrect.
• Did Gregor Mendel’s work involve balanced and unbalanced forces?
No, Gregor Mendel’s work was in the field of genetics. Answer B is incorrect.
• Did Isaac Newton’s work involve balanced and unbalanced forces?
Yes, Isaac Newton developed three laws of motion that describe how balanced and unbalanced forces
affect the motion of an object. Answer C is correct.
• Did Watson’s and Crick’s work involve balanced and unbalanced forces?
No, the work of Watson and Crick focused on the double-helix structure of the DNA molecule and
base-pairing rules. Answer D is incorrect.
Question 2
Which of the following conclusions is based on the data in the table?
• Does the table show no pattern between balanced and unbalanced forces?
No, the table shows a pattern. All the balanced forces show equally sized arrows (forces) moving in
opposite directions. The unbalanced forces are either equally sized arrows (forces) moving in the same
direction or unequal forces moving in different directions. Answer F is incorrect.
• Are balanced forces equal and opposite in direction, while unbalanced forces can be different
sizes in the same or opposite directions?
Yes, the pattern in the table supports this answer choice. Answer G is correct.
• Are forces always equal and opposite in direction for both balanced and unbalanced forces?
No, according to the pattern in the table, balanced forces are equal in size and opposite in direction.
Unbalanced forces are not always equal in size and opposite in direction. Unbalanced forces can be of
different sizes and can be in the same direction. Answer H is incorrect.
• Can balanced forces be different sizes in the same or opposite direction, while unbalanced
forces are equal and opposite in direction?
No, balanced forces are always equal in size and opposite in direction, while unbalanced forces can
be of different sizes in the same or opposite directions. Answer J is incorrect.
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Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Question 3
Which example does NOT exhibit unbalanced forces?
• Does answer choice A show an unbalanced force?
Yes, both forces are pointing in the same direction; therefore, they are unbalanced. Answer A
is incorrect.
• Does answer choice B show an unbalanced force?
Yes, the arrows show unequal forces in opposite directions; therefore, they are unbalanced.
Answer B is incorrect.
• Does answer choice C show an unbalanced force?
No, the forces are of equal size and in opposite directions; therefore, they are balanced. Answer C
is correct.
• Does answer choice D show an unbalanced force?
Yes, both forces point in the same direction; therefore, they are unbalanced. Answer D is incorrect.
Question 4
Which illustration shows an unbalanced force causing a change in motion?
• Does a person lying in bed show a change in motion?
No, there is no change in motion when a person is lying on a bed; therefore, it cannot be an
unbalanced force. Answer F is incorrect.
• Does a car parked on a road show a change in motion?
No, if the car is parked on a road, there is no change in motion and the forces are balanced.
Answer G is incorrect.
• Does an astronaut floating in space show a change in motion?
No, there is not a force shown that would represent a change in motion of the astronaut. Answer H
is incorrect.
• Does a baseball hitting a bat show a change in motion?
Yes, the bat connecting with the ball causes a change in the ball’s motion; therefore, the forces are
unbalanced. Answer J is correct.
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Question 5
Which statement best describes the motion of the surfer?
• Is the surfer traveling to the left? Is the speed increasing due to net force of 105 N?
Yes, the surfer will travel to the left because the force arrows indicate the direction of motion. The
speed increases because the wave increases the speed of the surfer. The forces will be added
because both arrows are moving in the same direction. When added, 100 N and 5 N equals 105 N.
Answer A could be the correct answer but check all answer choices.
• Is the surfer traveling to the right? Is the speed increasing due to net force of 105 N?
No, the surfer will travel to the left because all force arrows point to the left. Answer B is incorrect.
• Is the surfer traveling to the left? Is the speed constant due to net force of 105 N?
Yes, the surfer will travel to the left because the force arrows indicate that is the direction of motion.
The speed is not constant because the wave changes the speed of the surfer’s motion. Answer C
is incorrect.
• Is the surfer traveling to the right? Is the speed constant due to net force of 105 N?
No, the surfer will travel to the left because all force arrows point left. The speed is not constant
because the wave changes the speed of the surfer’s motion. Answer D is incorrect.
Question 6
What happens to the speed and direction of the car?
• Will the car move forward with a force of 10 N with a constant speed?
No, the friction force is in the opposite direction. When forces are in opposite directions, they are
subtracted; the car will move forward with a force of 7 N. Answer F is incorrect.
• Will the car move forward with a force of 7 N with an increasing speed?
Yes, the forces are in opposite directions, so they will be subtracted. When 3 N is subtracted from
10 N, the result is 7 N in the forward direction. The speed is increasing because the motion of the car
changes from rest to moving. Answer G is correct.
• Will the car move backward with a force of 10 N with an increasing speed?
No, the car will move forward because the greater force is pushing it in that direction. Answer H
is incorrect.
• Will the car move backward with a force of 7 N with a constant speed?
No, the speed will not be constant because the motion of the car changes from rest to moving in the
forward direction. Answer J is incorrect.
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Interventions
Teacher Instructions
After assessing student learning, use the following activities to provide remediation.
Pendulum versus Swing
Have students compare the force required to start a pendulum in motion to the force required to start
a swing in motion. Make a pendulum to observe objects that swing. Take the class to a playground
and observe the force it takes to start a swing and to keep a swing in motion. Discuss as a class how
unbalanced forces change the speed or direction of the object’s motion.
Pulley Motion
Have students build simple pulley systems with dowel rods or pencils, spools, string, and various
objects to lift as loads. To build a pulley, thread the spool onto the dowel rod or pencils. Twist the spool
to make sure it moves freely. Have two students hold each end of the dowel rod. Have students tie a
load (toy car, small bathroom cup, etc.) to one end of the string. Before measuring the force to lift each
load, ask students to form testable hypotheses about which load will require more force to lift. Ask
students to measure the amount of force used to lift the loads using a spring scale.
Discuss how unbalanced forces change the speed or direction of the object’s motion.
Extending Student Thinking
Teacher Instructions
After assessing student learning, use the following activity to provide enrichment.
Have students research the history of toys, such as pull toys or wagons, spring toys, and pull cars. Have
students design a fold-book to explain when the toy was invented, how it changed over time, and how
unbalanced forces relate to the movement of the toy.
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Answer Codings
(student pages 73–78)
Page
#
73
74
75
76
77
78
Question
#
Process
TEKS
Answer
Bloom’s Original/Revised
DOK
Level
ELPS
Activity 1
Answers may vary. An example is shown.
Tug-of-war – The arrows show that the unbalanced force
will pull the rope and people to the right, because the greater
force is towards the right.
Chair moving – The arrow shows that the unbalanced force
will move the chair to the right.
Ball moving – The arrow shows that the unbalanced force
will cause the soccer ball to move to the left and up.
Toy truck moving – The arrows show that the unbalanced
forces will cause the toy truck to move to the right.
8.1(A)
8.2(B)
8.2(D)
8.2(E)
8.4(A)
8.4(B)
Application/Apply
3
(c)1.C
(c)2.I
(c)3.E
(c)4.G
(c)5.F
Activity 2
Number of Washers
Answers may vary, but as the number of washers increases,
the force will increase and the speed will decrease.
Yes, as the number of washers increased, the speed
decreased. Ten washers moved at a slower relative speed than
six washers.
Type of Surface
Forces – Answers may vary. Relative Speed – Carpet: Very
slow, Concrete: Slow, Sandpaper: Slow, Smooth surface: Fast
The more texture a surface has, the greater the unbalanced
force required to move the washers.
Friction
Force of Friction: Answers may vary.
Force of Surface: Answers may vary.
Diagrams may vary.
8.1(A)
8.2(B)
8.2(D)
8.2(E)
8.4(A)
8.4(B)
Analysis/Analyze
3
(c)2.I
(c)3.E
(c)4.G
(c)5.F
(c)4.I
1
C
8.3(D)
Comprehension/Understand
2
2
G
8.2(E)
Analysis/Analyze
3
(c)4.J
3
C
Application/Apply
2
(c)4.J
4
J
Analysis/Analyze
2
(c)4.J
5
A
Application/Apply
2
(c)4.J
6
G
Application/Apply
2
(c)4.K
1
100
Application/Apply
1
(c)4.J
2
F
Comprehension/Understand
3
(c)4.I
3
D
Comprehension/Understand
2
(c)4.I
4
J
Application/Apply
2
(c)4.J
5
C
Application/Apply
2
(c)4.J
6
H
Application/Apply
2
(c)4.J
7
B
8.2(C)
Comprehension/Understand
2
(c)4.I
8
H
8.2(E)
Analysis/Analyze
2
(c)4.J
9
D
8.2(B)
Application/Apply
3
(c)4.J
10
G
8.3(C)
Analysis/Analyze
2
(c)4.J
11
C
8.2(B)
Application/Apply
2
(c)4.J
12
F
8.4(B)
Application/Apply
1
(c)4.I
13
B
8.4(A)
Application/Apply
1
(c)4.I
14
J
8.2(E)
Application/Apply
2
(c)4.J
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Teacher Edition Sample Page
Unit 7
Unbalanced Forces
Readiness Standard – 8.6(A)
Answer Codings
(student pages 79–82)
Page
#
79
80
Question
#
82
116
DOK
Level
Bloom’s Original/Revised
ELPS
Answers may vary.
Answers may vary, but students should articulate that
unbalanced forces create sudden changes in speed and
direction. These sudden changes allow the human body
to experience g-forces and other sensations, creating
thrill and excitement.
8.2(C)
8.2(E)
8.3(B)
Synthesis/Create
3
(c)1.C
(c)1.E
(c)5.B
(c)5.G
Answers may vary but should show another arrow
in the graphic with a size. Students should be able
to describe how the force will speed up (arrow in
the same direction), slow down (arrow in opposite
direction), or change direction (any other arrow
direction besides same or opposite direction).
8.2(C)
8.2(E)
Application/Apply
2
(c)1.C
(c)5.B
Answers may vary. Some examples include seat belts
in cars, restraints on amusement park rides, etc.
8.2(C)
Synthesis/Create
3
(c)1.A
(c)5.G
Vocabulary
Activity
Definition – pushes or pulls that cause an object to move,
stop, or change direction
Illustration – Illustrations may vary.
Related words – Related words may vary but may include
change, balanced force, speed, direction, and/or motion.
Examples – Examples may vary but may include
bouncing a basketball, braking on a bicycle, and pedaling
faster on a bicycle.
Non-examples – Non-examples may vary but may
include balancing a basketball on your finger or stabilizing
a bicycle while standing.
Sentence – Sentences may vary. Unbalanced forces
allow scientists to explore outer space through the use of
rockets, which launch astronauts and scientific equipment
into space.
8.2(C)
Comprehension/Understand
2
(c)1.C
(c)5.B
(c)5.F
Homework
Examples may vary.
All unbalanced forces require a force large enough to
change the motion of an object. The change can be
from rest to moving, moving to rest, or the direction in
which the object is moving.
8.1(A)
8.1(B)
8.2(A)
8.2(C)
8.2(E)
8.3(B)
8.4(A)
8.4(B)
2
(c)1.A
(c)1.C
(c)2.E
(c)3.D
(c)5.B
Critical
Thinking
Formative
Assessment
Science
Journal
81
Process
TEKS
Answer
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