FORCE AND MOTION
UNIT OVERVIEW Force and motion are fundamental to all matter in the universe. A force is
anything that can push or pull an object. Forces influence objects that are
at rest or that are already in motion. The Force and Motion unit acquaints
students with Isaac Newton’s three laws of motion, which describe how
forces interact with objects to influence motion. These laws involve inertia,
mass, velocity, and momentum. Students will learn about several key forces,
including gravity, friction, and magnetism. A force is required to do work,
and generating a force requires energy. Energy can be stored as potential
energy, or it can have kinetic energy—the energy of motion. Energy can
also be converted and exchanged through energy transfer.
Certain reading resources are provided at three reading
levels within the unit to support differentiated instruction.
Other resources are provided as a set, with different titles
offered at each reading level. Dots on student resources
indicate the reading level as follows:
low reading level
middle reading level
high reading level
THE BIG IDEA
orces and motion are integral parts of our daily lives. From kicking a soccer
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ball to picking up a sandwich to dropping a pencil, force and motion are
always at play. Even the blood flowing through our bodies moves due to
the pumping force of the heart muscle. Objects move in predictable ways,
as described by the universally accepted principles of force and motion.
Everything is in constant motion because forces are always at work. Even
something that is at rest on Earth is orbiting the Sun and being acted upon
by gravity. By learning about force and motion, students will come to
understand how they can use forces to produce motions that allow them
to be safe and to enjoy themselves.
Other topics
This unit also addresses topics such as: force and motion in sports,
weightlessness, potential and kinetic energy of rubber bands, how gravity
affects the motion of objects in the solar system, perpetual motion, the forces
that move a roller coaster, and how racecars are built to maximize acceleration.
SPARK
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he spark is designed to get students thinking about the unit’s topics and
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to generate curiosity and discussion.
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Force and Motion
UNIT GUIDE
Materials
n
uncooked eggs
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hard-boiled eggs
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paper towels
Activity
Place students in small groups. Give each group one uncooked egg and one
hard-boiled egg without revealing which egg is which. Instruct students
to carefully place the two eggs on a table and to gently spin them without
letting either egg fall off the table. Have students observe the motion of
the eggs until they eventually come to rest. Students may notice that it is
more difficult to spin one of the eggs (the uncooked egg).
Now ask students to spin each egg again. Once both eggs are spinning, have
students quickly yet gently touch the top of each egg to stop it from spinning
and then let go. Direct students to continue watching the eggs and observe
what happens. The hard-boiled egg should remain stationary, but the
uncooked egg should begin to spin again after it is stopped.
Below are questions to spark discussion.
What made the eggs start spinning?
Why did both spinning eggs eventually come to rest, even when left untouched?
Was one egg more difficult to spin than the other? Why?
Did one of the eggs start spinning again after it was stopped? If so, why?
What would have happened if one of the eggs had moved past the edge
of the table? Why?
Using this experiment, how can you distinguish between uncooked and
hard-boiled eggs in the future?
Use this activity to begin an introductory discussion about force and motion.
Explain that inertia is the tendency for an object at rest to remain at rest and
the tendency for an object in motion to remain in motion. In this spark, the
liquid parts of the uncooked egg had more inertia than the solid, hard-boiled
egg. Because of inertia, the uncooked egg resisted spinning and also resisted
stopping once it was in motion. When the two eggs were forced to stop, the
inertia of the liquid egg started the egg spinning again. Eventually, though,
both eggs lost their momentum, stopped spinning, and came to rest. This
was due to a force called friction acting against the motion of the eggs.
Throughout the unit, students will learn more about forces and motion.
Many of the unit’s vocabulary terms are related to the spark activity and can
be introduced during the spark. For vocabulary work, see the Vocabulary
section in this Unit Guide.
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Force and Motion
UNIT GUIDE
PRIOR
KNOWLEDGE
I nvite students to explain their understanding of force and motion. Also ask
them to share what they know about friction, inertia, momentum, and mass.
Discuss how our world would be different without forces acting on objects.
Probing Questions to Think About
Use the following questions to have students begin thinking of what they
know about force and motion.
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hat is an example of a force?
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Can nature act as a force to move objects? If so, what are some examples?
Why do objects fall to the ground?
Is it possible to make a machine that continues to run forever
(perpetual motion machine)?
Why is it harder to pick up a brick than a pencil?
Why do objects you throw always seem to fly in an arch?
Why does a bicycle speed up as it rolls downhill?
Is it harder to turn a corner at a slow or a fast speed? Why?
Why is it easier to pull a wagon on a sidewalk than on grass?
Why do you sometimes feel a floating sensation on a roller coaster?
Would your weight be the same on the Moon as on Earth?
Tell students they will learn more about these topics soon.
UNIT MATERIALS Each unit provides a wide variety of resources related to the unit topic.
Students may read books and other passages, work in groups to complete
hands-on experiments and investigations, discuss science ideas as a class,
watch videos, complete writing tasks, and take assessments.
Resources are available for printing or projecting, and many student
resources are also available for students to access digitally on
.
Selected unit resources are available in more than one language.
For a complete list of materials provided with the unit, see the Force
and Motion unit page on the Science A–Z website.
VOCABULARY Use the terms below for vocabulary development throughout the unit.
Cut or Fold
Force and Motion
Force and Motion
attract
(verb)
to pull toward
WORD CARD
DEFINITION CARD
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Force and Motion
Force and Motion
balanced
(adjective)
in a state in which equal
and opposite forces
cancel each other out
WORD CARD
They can be found in boldface in the Nonfiction Book, the Quick Reads,
and/or other unit resources. These terms and definitions are available
on Vocabulary Cards for student practice. Additional vocabulary lists are
provided in the teaching tips for Investigation Packs and FOCUS Books.
DEFINITION CARD
$
Force and Motion
Force and Motion
chemical energy
(noun)
energy made by a
change in a substance
or a combination
of substances
WORD CARD
© Learning A–Z All rights reserved.
DEFINITION CARD
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Force and Motion
UNIT GUIDE
Core Science Terms
These terms are crucial to understanding the unit.
direction
t he way or course toward which something moves
or faces
distance
the amount of space between things
electromagnetism
the combined force of electricity and magnetism
energy transfer
t he movement of energy from one object to another
or the change of energy from one form to another
force
the strength or energy that moves an object
friction
a force that slows down moving things
gravity
t he force that pulls things toward the center of Earth
or any other object that has mass
inertia
t he tendency of an object to resist change in the
direction or speed of its motion
kinetic energy
the energy that a moving body has because of its motion
magnetism
a force that pushes and pulls certain metals
mass
the amount of matter, measured on Earth by its weight
momentum
the strength or force that keeps something moving
motion
the act of going from one place to another; movement
potential energy
t he energy a body has because of its position, electrical
charge, or structure; stored energy
speed
the rate of movement
weight
ow heavy something is, determined by the pull
h
of gravity on the object’s mass
work
t he act of using force to move something over
a certain distance
Other Key Science Terms
The following vocabulary is not essential for comprehending the unit
but may enrich students’ vocabulary.
© Learning A–Z All rights reserved.
attract
to pull toward
balanced
i n a state in which equal and opposite forces cancel
each other out
chemical energy e nergy made by a change in a substance
or a combination of substances
electricity energy created by moving charged particles
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Force and Motion
UNIT GUIDE
energy the power to do work, make a change, or move objects
engine a machine with moving parts that uses power to create
motion; a motor
generator a machine that turns potential and kinetic energy
into electricity
heat energy a form of energy that is transferred from an object
with a higher temperature to an object with a lower
temperature
law a statement about results that always occur under
certain circumstances
light energy a form of radiant energy that allows us to see
lines of force i nvisible lines of magnetic force that flow through
and around a magnet
magnetic field a n area around a magnet or a moving electrical
charge within which a magnetic force acts
reaction an equal, opposite response to a force being applied
repel to force or push away
rest a pause during which no force is moving an object
sound energy a form of energy that allows us to hear
velocity
the rate of movement in a certain direction
weightless experiencing little or no noticeable gravitational pull
Vocabulary Activities
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You may choose to introduce all the terms that will be encountered in the
unit before assigning any of the reading components. Vocabulary Cards with
the key science terms and definitions are provided. Dots on the cards indicate
the reading levels of the Nonfiction Book or the Quick Reads in which each term
can be found. If all level dots appear, the term may come from another
resource in the unit. Students can use these cards to review and practice the
terms in small groups or pairs. The cards can also be used for center activity
games such as Concentration.
The Word Work activity sheets offer fun puzzles and practice with key
vocabulary terms from the unit. For further vocabulary practice and
reinforcement, you can choose from the vocabulary Graphic Organizers.
To build customized vocabulary lessons with terms related to the topic,
see
.
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Credit:
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Force and Motion
UNIT GUIDE
Students can use the Word Smart vocabulary Graphic Organizer to organize
information on the science terms. You may want to assign each student
one to three words to share his or her Word Smart knowledge with classmates.
Students who have the same word should first compare their Word Smart
sheets with each other and then report to the larger group.
The science terms can be used in oral practice. Have students use each
term in a spoken sentence.
As students read, encourage them to create a science dictionary by recording
new vocabulary terms and definitions in their SAZ Journal.
BACKGROUND and Use this section as a resource for more background knowledge on unit
MISCONCEPTIONS content and to clarify the content for students if misconceptions arise.
Refer to Using the Internet below for more ways to extend the learning.
Q: If a body in motion remains in motion until a force acts on it, why do things
eventually stop? Is it because they used up all their energy?
Force and Motion
A Science A–Z Physical Series
Word Count: 2,299
Written by Ned Jensen
Visit www.sciencea-z.com
www.sciencea-z.com
A: Objects eventually stop because a force—such as friction or gravity—
acts against the object’s motion. Once an object is in motion, the energy
that was used to initiate the motion is irrelevant. In the absence of forces
acting against that motion, a moving object would, in fact, continue to
move forever! This is true of a bouncing ball, a speeding car, a galloping
horse, and a shooting star.
Q: If I want to keep an object moving, do I need to keep applying a force?
A: In theory, no. According to Newton’s first law, a body in motion will
remain in motion. An object will keep moving at the same velocity as long
as it doesn’t receive any additional pushes or pulls. Objects do not stop
because of a lack of force; they stop because a different force is being
applied. For example, friction is a force that acts against an object’s motion.
If you slide a book across a table, it will eventually come to rest because
friction is pushing on it in the opposite direction of its motion. Reducing
friction by applying oil or flour to the table would allow the book to travel
farther given the same amount of force.
Q: Are speed, velocity, and acceleration the same thing?
A: No. They are related but are not exactly the same. Speed measures the
rate of motion—how fast something is going. Velocity is the speed an object
is moving in a certain direction. Acceleration is the measurement of the change
in velocity over time. A change in acceleration can be a change in an object’s
speed or direction. According to Newton’s second law, a force is required to
accelerate an object.
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Force and Motion
UNIT GUIDE
Q: When an object is at rest, are any forces acting on it?
A: Yes. Even when an object is stationary, the force of gravity is pulling it
toward Earth’s center. Friction is helping to hold it in place against a surface.
At the same time, whatever the object is sitting on opposes the force of gravity
and holds the object up. This force is called the normal force. In addition, other
forces, such as air movement, could be acting on the object but are not strong
enough to overcome the object’s inertia.
Q: Do heavier objects fall to the ground faster than lighter object?
A: No and yes. In the absence of air resistance, objects of all sizes and weights,
when dropped from the same height, will hit the ground at the same time.
Without air resistance, objects experience free fall. During free fall, objects
with more mass experience greater force due to gravity, but this greater force
is offset by the increased inertia of the larger mass. Because of this tradeoff,
the objects hit the ground at the same time. In the presence of an appreciable
amount of air resistance, more massive objects will fall faster than smaller
objects. In this case, air resistance is strong enough to slow down smaller
objects, whereas the larger, more massive objects continue to accelerate. Also,
objects of similar mass will fall at different rates if one encounters more air
resistance than the other due to its shape. This is the case when comparing
the drop rate of a crumpled paper and a paper airplane.
Q: Why do astronauts on a space station orbiting Earth float?
A: Astronauts look as though they are floating, but they are actually falling.
Free fall occurs when gravity is the only force acting on objects. In free fall,
no contact forces are acting to oppose the force of gravity. The space station,
the astronauts, and all the objects within the space station are falling together
at the same rate in a curved pattern, or orbit, so the people are not held
down as they would be on Earth. This is why astronauts feel weightless
in space.
Q: Is there gravity in outer space?
A: Yes, definitely! There is some amount of gravity everywhere in outer space.
Gravity is what keeps planets in orbit around the Sun and what keeps the
Moon in orbit around Earth. Gravity is an attraction between two objects.
Larger masses have stronger gravitational pulls. The Moon’s gravity is strong
enough to create ocean tides on Earth. The Sun is so large that its gravitational
pull reaches beyond our own solar system. Even entire galaxies exert gravity
on one another. However, this pull decreases as the distance between two
masses increases.
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Force and Motion
UNIT GUIDE
Q: Is it true that I would weigh less if I were standing on the Moon?
A: Yes. Weight is a measurement of the amount of force an object exerts
because of gravity. The more massive something is, the more gravitational
pull it exerts. If you step on a scale, you are basically squeezing the springs
in the scale between yourself and the floor, gravity is pulling you down,
while the force of the floor is pushing you up (normal force). The more mass
you have, the more you squeeze the springs of the scale, so the more you
weigh. On the Moon, the force of gravity is one-sixth as strong as the force
of gravity on Earth. Since the force of gravity is weaker on the Moon, it
would pull down on you much less than the force of gravity on Earth.
If you were to step on the same scale on the Moon, you would squeeze
the springs less and therefore weigh less. Your mass would not change,
but your weight would. If you could stand on Jupiter, you would weigh
much more than on Earth.
© Jupiterimages Corporation
EXTENSION
ACTIVITIES
Using the Internet
Most search engines will yield many results when the term force or motion is
entered. You can also perform a more specific search, such as for information
on Isaac Newton and his three laws of motion. Be aware that some sites may
not be educational or intended for the elementary classroom. More specific
inquiries are recommended, such as:
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force and motion in sports
Galileo’s theories of motion
law of universal gravity
electricity and magnetism
energy and work
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inertia and momentum
physics for kids
friction in shoes
weightlessness
kinetic vs. potential energy
Below are some links with excellent resources for students and/or teachers.
Rader’s Physics4Kids website is written for children and contains explanations
of force, acceleration, motion, energy, work, and mass. The site also contains
quizzes for students to assess their knowledge of force and motion.
www.physics4kids.com/files/motion_intro.html
Physics in Sports Connection uses athlete video clips to explain and illustrate
Newton’s law of universal gravity and his three laws of motion. The site
includes questions about the video clips that will stimulate student thinking
about force and motion.
http://archive.ncsa.illinois.edu/Cyberia/VideoTestbed/Projects/NewPhysics/page_1.html
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Force and Motion
UNIT GUIDE
Read all about Newton’s laws on the NASA website designed for educators
and students. This site includes grade-specific links to suggested force and
motion activities and demonstrations, plus a page for students at a lower
reading level. www.grc.nasa.gov/WWW/K-12/airplane/newton.html
Kids will enjoy learning about the physics of skateboarding on this website
published by the Exploratorium in San Francisco. Like all other objects,
Newton’s Laws—as well as friction and momentum—apply to skateboards.
www.exploratorium.edu/skateboarding
The UCLA Physics & Astronomy K–6 Connection is published by two
scientists with the goal of bringing astronomy and physics into elementary
classrooms. It supplies teachers with the knowledge they need to teach
students. Click on the Physics Table of Contents link to reach content about
force and motion. The site includes teaching tips and classroom activities.
www.physics.ucla.edu/k-6connection
The Physics Classroom website presents tutorials that explain force and
motion with helpful illustrated diagrams. The site also contains worksheets
and activities that can be used in the classroom. Some content may be
too advanced for elementary school students or may require additional
instruction. www.physicsclassroom.com/Class
Projects and Activities
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© Learning A–Z All rights reserved.
Inquiry Science/Project: Take students outside to the school playground.
Ask them to observe common playground equipment such as a swing
set, a teeter-totter, and a slide. Have students choose one piece of
playground equipment and design a hypothetical experiment on force
and motion that improves the way the equipment works. For example,
increasing the length of the chains on a swing will increase the maximum
height a rider can reach. Adding a lubricant to a slide will reduce friction
and allow the rider to go faster.
Inquiry Science/Project: Experiment with the relationship between
force, mass, and acceleration (refer to Isaac Newton’s famous equation,
F = m × a). Use balls of various sizes and weights (for example, PingPong, golf, tennis, and baseball). Drop the balls from various heights
into smoothed sand, such as from the top of a play structure in a
playground. Balls with more mass will cause larger impact craters
in the sand than balls with smaller mass. In addition, dropping balls
from a greater height will cause them to accelerate more and will
cause larger impact craters in comparison to balls dropped closer
to the ground. Measuring the width and depth of the impact craters
will give students a means of comparing the amount of force that was
applied to the ground when each ball struck it.
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Force and Motion
UNIT GUIDE
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© Learning A–Z All rights reserved.
riting: Have students write a brief biography of Isaac Newton.
W
Encourage them to include dates of his important discoveries and
events in his life that may have influenced his thinking on force and
motion. For more information on writing biographies, visit
.
Guest: Invite a physicist or engineer to the classroom to discuss force
and motion and how it impacts our daily lives. Ask the speaker to focus
on an everyday item, such as a car, and how engineers work to reduce
friction and drag so that cars can do more work using less fuel for energy.
Arts: Have students view paintings related to forces and motion, such
as The Hammer and the Feather by Alan Bean (www.alanbeangallery.com/
hammerfeather-new.html). Ask them to describe what is happening in
each painting and what concept(s) of force and motion each painting
is illustrating. Supply students with colored pencils, markers, paint,
and construction paper so they can make their own version of a
famous painting.
Technology: Invite students to explore the following website:
http://phet.colorado.edu/sims/projectile-motion/projectile-motion_en.html.
This simulation allows students to launch various projectiles at a
target. Students can experiment with changing variables such as
initial speed, mass, and diameter of the object as well as whether
or not wind resistance is present during the simulation.
Field Trip: Attend a sporting event, such as a soccer game or a gymnastics
competition. Have students take notes and record sketches of forces and
motion they observe. Back in class, encourage them to share and explain
their examples using Newton’s laws of motion.
Research/Home Connection: Students can conduct
research as a family/home project or in the library/
media center to extend the learning about a topic
in one of the Quick Reads or other unit resources.
10
www.sciencea-z.com