Download Name _____Answer Key____ 1. force ____Any push or pull that

Name _____Answer Key____
Date _________________
F. Energy and Motion
Chapter 1—Forces
STUDY GUIDE
Lesson 1: What Forces Affect Objects on Earth Every Day?
A. Vocabulary—Write the definition to each word below.
1. force ____Any
push or pull that causes an object to move, stop, or change
direction
2. friction_____A
force that opposes or act against motion when the surfaces rub
against each other
3. magnetism_____The
force of repulsion (pushing) or attraction (pulling) between
poles of magnets
4. gravitation_____The
force that pulls all objects toward each other
B. Answer the following questions in complete sentences.
1. What is a force?
A push or pull that can move, stop, or change the direction of
an object.
2. What three forces affect Earth and objects on Earth every day?
a. __friction
b. ___magnetism
c. ____gravity
3. What starts an object moving or stops it if it is already moving? __A
Force starts an object
moving.
4. What force keeps the moon in orbit around Earth? ___Gravity
or gravitation keeps the
The direction would be east.
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5. Suppose you push a cart toward the west. In what direction does the force of friction push on the
cart’s wheels?
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moon in orbit around the Earth.
Multiple Choice:
6. The force of gravitation between two objects is less when:
A.
B.
C.
the total of their masses is greater
friction between them is greater
the force of magnetism is greater
D.
the distance between them is greater
C. Complete each sentence below by writing the word friction, magnetism, or gravitation in the
blank:
1. The moving parts of an automobile engine are coated in oil or grease to reduce the
__friction__ between the metal parts.
2. Some toys let you draw hair, eyebrows, and other features with a special wand that moves iron filings
around by ____magnetism______.
3. A balance scale works by using ______gravitation______ to compare the weights of two objects.
4. A parachute uses the force of air pushing up on a large area of silk to resist the force of
____gravitation_______.
5. When you apply the brakes on your bike, you are clamping down on the bike’s wheel to increase the
force of ____friction_________.
6. Hikers can use a compass to guide them along a trail because a compass needle is pulled to the north
by ____magnetism________.
7. You can tape lightweight objects to a wall, but if you try to tape something heavy to a wall and it falls
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off, you’ll know the tape isn’t strong enough to overcome the force of ___gravitation____.
Lesson 2: What are Balance and Unbalance Forces?
A. Vocabulary—Write the definition to each word below.
1. balanced forces____equal
in size, as the result they cancel each other out
2. unbalanced forces____one
force is greater than the opposite force,. A change in
motion occurs.
3. acceleration___change
in motion caused by an unbalanced forces or a change
in velocity
4. net force ____combined
total of forces. Adding or subtracting the individual
forces give a value or net force
B. Answer the following questions in complete sentences.
1. What happens to an object’s motion when unbalanced forces act on it?
When unbalanced forces act on it, the object’s motion changes.
2. If you see an object change its motion, what has happened to it? _An
object changes its
motion if a force or forces have acted on it.
3. What is the net force when a force of 100 newtons pushes against a force of friction of 80 newtons?
The net force will be 20 newtons.
4. What happens to an object when balanced forces act on it? __When
balanced forces act on
an object, nothing happens.
5. A moving object speeds up. Are the forces acting on the object balanced? Explain.
No, because acceleration is taking place.
6. Suppose you ride a bike along a flat, straight road at a constant speed. Are the forces acting on the
bike balanced or unbalanced? Explain. ____The
forces acting on the bike are balanced.
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We know that a force has acted on both cars because the motion of both cars
has changed.
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7. Two bumper cars collide. Both cars stop. How do you know that a force has acted on both cars?
Multiple Choice:
8. Suppose a book weighs 35 newtons and you apply a force of 50 newtons to lift it. The net force
acting on the book is:
A.
B.
85 newtons, up
50 newtons, up
C.
15 newtons, up
D.
35 newtons, down
C. Decide whether the underlined term or phrase makes each statement true or false. If the
statement is true, write the word true on the line. If the statement is false, write the word false on
the line and write a word or phrase that makes the statement true.
________True____________ 1. Balanced forces are equal in size and opposite in direction and
therefore cancel each other out.
________True___________ 2. The change in motion of an object is always caused by a force or forces.
______No
force_________ 3.
If balance forces are acting on an object, it will seem as if a net force is
acting on the object.
_______in
pairs_________ 4.
adding or subtracting_ 5.
Forces always act alone.
Balancing the forces acting on an object gives you the net force.
____unbalanced_______ 6. When balanced forces act on an object, the object speeds up, starts to
move, slows down, stops, or change direction.
_______True____________ 7. If two equal forces act on an object in opposite directions, the net force
will be balanced.
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_______True____________ 8 Unbalance forces can stop a moving object.