Download Laws of Motion Review KEY

Name________________________ Period _______
Chapter 2 The Laws of Motion Review
Describe the relationship between gravitational force and distance as shown in the diagram.
Assess the information about gravity, mass, and weight.
Read each statement. If it is true, write T in the center column.
If it is false, write F in the center column and replace the underlined
words to make the statement true.
Statement
Mass is a gravitational force exerted by
an object.
An object’s weight is proportional to
its mass.
Mass is measured in newtons.
If an object has twice the size of
another object, it has half the weight.
An object’s mass decreases the
farther it gets from Earth’s surface.
Corrected Statement
FALSE: Weight is the gravitational
force
TRUE
FALSE: Mass is measured in kg
FALSE: Mass and Twice the weight
FALSE: Weight
Summarize Newton’s first law of motion.
If the net force on an object is zero, an object at rest ______Will Stay at Rest____,
an object at motion ______Will Stay in Motion_____________.
Explain the effect of inertia on objects at rest and objects in motion.
Inertia is the tendency of an object to resist change. Latin for LAZY
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Summarize how friction and inertia act on an object sliding on a flat surface.
Inertia causes a moving bject to keep moving,
while friction will slow an objects motion
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Identify 2 characteristics of motion that can be changed by forces.
1.___________SPEED_____________
2. ________DIRECTION________________
Draw the described forces. Use labeled arrows to indicate the forces on a box,
and show the net forces in the column to the right.
Description
Net force
1. A force of 200 N to the
left and another force of 50
N to the left
250 N to the LEFT
2. A force of 100 N to the
right and a force of 80 N to
the left
20 N to the RIGHT
3. A force of 180 N to the
right and a force of 180 N to
the left
0N
Identify the forces in the table above as balanced forces or
unbalanced forces.
1. ___Unbalanced_____________________________________
2. ___Unbalanced ___________________________
3. ___Balanced ___________________________
Summarize Newton’s first law of motion
If the net force on an object is zero, an object at rest
___________________________________,
an object at motion ____________________________________________.
Explain the effect of inertia on objects at rest and objects in motion.
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Summarize how friction and inertia act on an object sliding on a flat surface.
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Cite the effect of forces on an object at rest.
Force
Effect
Balanced
Object remains at Rest
Unbalanced
Object is set in Motion
Describe the effect of forces on an object in motion.
Force
Effect
In the direction of the object’s motion
Object will speed up or maintain constant speed
In the direction other than that of the
object’s motion
Object slows down or changes direction
Recall the difference between velocity and acceleration.
Velocity
Speed & Direction
Acceleration
A change in Velocity
Summarize Newton’s second law of motion
The _____ACCELERATION_____________of an object is equal to the
______NET FORCE____________exerted on the object divided by an object’s mass.
Explain the equation for Newton’s second law.
a stands for 
__acceleration_____
_____m/s2___________
a = F/m


m stands for
____mass______
____kg________
Predict the corresponding result for each force.
F stands for
___Force_____
______N__________
Force
Result
An airplane’s jet engine pushes air
toward the back of the plane.
Air pushes back, plane moves forward.
A fisherman tosses an anchor away
from his boat.
Anchor applies force on the fisherman and
his boat, pushing them in the opposite
direction
Ground pushes back and moves the skier
A skier digs ski poles into the snowy
ground and pushes down and backward. forward
Summarize Newton’s third law of motion in your own words.
When one object applies a force on another object, the second object applies the same, but
opposite force back.
Define the 2 parts of a force pair
1. _____ACTION__________
2. _____REACTION__________
Analyze why force pairs do not cancel each other.
Equal and opposite forces

__________ Net Force
Classify forces in the sentences below. Underline action forces; circle reaction forces.
A swimmer pushes his arms back against the water in a pool, and the water pushes forward
against his arms.
A rocket engine pushes hot gas out in a downward direction, and the hot gas pushes upward
on the engine.
A trampoline hurls a girl into the air.
Model Newton’s third law of motion in a drawing. Label these terms:
• action force
• force
• force pair
Define momentum.
The measure of how hard it is to stop a moving object
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Momentum: Circle the object that would be more difficult to stop.
A 10-kg shopping cart moving at 5 m/s
or
2-kg ball moving at 28 m/s
If you have ever been in a car at a stoplight beside a large truck, you probably noticed that
the car took off from the stop much more quickly than the truck. Explain why it is harder to
start and stop the motion of a large truck than that of a small car.
The truck has a greater mass than the car, so it requires more force to set it in motion.
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When it is in motion, its greater mass causes it to have more momentum,
making in harder to stop.
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