UNIT FORCE AND MOTION REVIEW

TEKS 6.7B, 6.7C,
7.7D

LOOK BACK PRESENTATION

Force, Motion, and
Acceleration

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What is Newton’s First Law of Motion?

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What is Newton’s First Law of Motion?

continued

A force is a push or a
pull. An object will stay
at rest or in uniform
motion unless acted
upon by an unbalanced
force. That tendency is
called inertia. Newton’s
first law of motion
states that an object
will maintain its state of
motion unless a force
acts upon it.

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How do unbalanced forces affect motion?

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How do unbalanced forces affect motion?

continued

Unbalanced forces
can move an object or
change the motion of
an object that is
already moving. The
more speed a moving
object has, the more
force is required to
change its motion.

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How do balanced forces affect motion?

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How do balanced forces affect motion? continued

Balanced forces produce a net force of zero if they
are acting on the same object. When an object is at
rest, the downward force of gravity is balanced by
other, upward forces.

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What are balanced and unbalanced forces?

Balanced Forces

Unbalanced Forces

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What are balanced and unbalanced forces?
continued

Balanced Forces

Unbalanced Forces

Two forces acting on an object that are equal in strength and
opposite in direction are balanced forces. Two forces that are not
equal in strength or opposite in direction are unbalanced forces.

Multiple Choice

A lamp sitting on a table.

• Balanced Force

• Unbalanced Force

Multiple Choice

A car accelerating around a mountain curve.

• Balanced Force

• Unbalanced Force

Multiple Choice

A skier skiing through flags in a race down the mountain.

• Balanced Force

• Unbalanced Force

Multiple Choice

What direction will this object move? 

• It won't move. 
• It will move to the right. 
• It will move to the left. 
• It will move up. 

Multiple Choice

Calculate the Net Force. 

• 60N, Left 
• 40N, Right 
• 0N
• 60N, Right

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How is net force calculated 1 continued

Forces Applied in the Same Direction

Net force is the combination of all
the forces acting on an object. If
the forces act in the same
direction, then the net force is the
sum of the forces.

A net force of zero means forces
are balanced and the object’s
position, motion, or shape does
not change.

A nonzero net force means that
the forces are unbalanced and
that the object’s position, motion,
or shape is changing.

Net force = 18 N + 12 N = 30 N

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How is net force calculated 1

Forces Applied in the Same Direction

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How is net force calculated 2

Forces Applied in Opposite Directions

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How is net force calculated 2 continued

Forces Applied in Opposite Directions

Net force = 18 N − 12 N = 6 N

Net force = 6 N − 5 N = 1 N

If the forces act in opposite directions, then the net force
is the difference in the strengths of those forces. Net
force is calculated the same way for forces exerted in a
horizontal direction and in a vertical direction.

Multiple Choice

Calculate the net force of the object in the image shown.

• 20N
• 35N
• 5N
• 25N

Multiple Choice

Students are playing tug-of-war. If group B pulls the rope to the right with a force of 400 N and group A pulls the rope to the left with a force of 250 N, what will happen to the ribbon in the middle of the rope?

• The ribbon will move to the left and group A will win the tug-of-war.
• The ribbon will move to the left and group B will win the tug-of-war.
• The ribbon will move to the right and group B will win the tug-of-war.
• The ribbon will move to the right and group A will win the tug-of-war.

Multiple Choice

What is the net force (calculation).

• 5

• 11 N Right

• 5 N Right

• 0 N

Multiple Choice

What is the net force?

• 5 N
• 45 N to the left
• 5 N to the right
• 45 N to the right

Multiple Choice

Two teams were having a tug of war. Team A had four people on the team, and each of them pulled with 25N of force. Team B had three people on the team, and each of them pulled with 35 N of force. Which team won, and how much greater was their net force on the rope?

• Team B by 10 N

• Team B by 30 N

• Team A by 20 N

• Team B by 65 N

Multiple Choice

What is the magnitude (size) and direction of the net force?

• 10 N to the Right
• 10 N to the Left
• 0 N
• 8 N to the Left

Multiple Choice

What is the magnitude (size) and direction of the net force?

• 21 N to the Left
• 3 N to the Left
• 21 N to the Right
• 3 N to the Right

Multiple Choice

What is the magnitude (size) and direction of the net force?

• 14 N Down
• 14 N Up
• 6 N Up
• 6 N Down

Multiple Choice

Omar and Katey reach for the same toy car at the same time. Omar pulls the toy away from Katey with a force of 10 N. Katey is pulling back with a force of 6 N. What is the net force?

• 4 N

• 6 N

• 10 N

• 16 N

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What is Newton’s Third Law of Motion?

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What is Newton’s Third Law of Motion?
continued

Newton’s third law of motion states that if one object
exerts a force on another object, then the second
object exerts an equal force on the first object in the
opposite direction.

The action-reaction forces described by Newton’s third
law are known as force pairs.

TEKS 8.7B, 8.5B

Newton’s Laws
of Motion

KEY IDEAS

• What are Newton’s laws?
• How do Newton’s laws explain motion

in systems?

Words to Know

system
Newton’s first law
Newton’s third law

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What are Newton’s Laws?

First
Law

Second
Law

Third
Law

Inertia

Force and
Acceleration

Action and
Reaction

A body at rest will remain at rest,
and a body in motion will remain
in uniform motion, unless acted
upon by an external force.

The force acting upon an object
is equal to the mass of an object
times its acceleration.

For every action there is an
equal and opposite reaction.

Newton’s Laws of Motion

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What are Newton’s Laws? continued

In a system, Newton’s laws of inertia, force, and reactions
apply and interact simultaneously. This is especially true of
real-world systems, including those that humans have
engineered.

Newton’s Laws of Motion

First
Law

Second
Law

Third
Law

Inertia

Force and
Acceleration

Action and
Reaction

A body at rest will remain at rest,
and a body in motion will remain
in uniform motion, unless acted
upon by an external force.

The force acting upon an object is
equal to the mass of an object
times its acceleration.

For every action there is an
equal and opposite reaction.

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Fix Newton’s Laws

Describe Provide new endings for the flawed statements
of Newton’s laws.

3.

For every action there is an equal reaction in the same direction.

1.

Objects that are motionless or have uniform motion tend to stay

that way unless the forces acting upon them are removed.

2.

Newton’s second law is represented by the equation F = m + a.

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Fix Newton’s Laws Answers

Describe Provide new endings for the flawed statements
of Newton’s laws.

1.

Objects that are motionless or have uniform motion tend to

stay that way unless the forces acting upon them are removed.

…unless an external force acts upon them.

2.

Newton’s second law is represented by the equation F = m + a.

… represented by the equation F = ma.

3.

For every action there is an equal reaction in the same direction.

… there is an equal and opposite reaction.

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How do Newton’s laws explain
motion in systems?

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How do Newton’s laws explain
motion in systems? continued

Bumper cars demonstrate
Newton’s three laws.

First Law: collisions with
unbalanced forces cause
changes in motion

Second Law: masses and
accelerations of the cars
determine the forces that
the riders feel

Third Law: one car strikes
another and the colliding
car bounces back

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Analyzing Motion in a System

AnalyzeGive examples of Newton’s laws in the system shown.

2.

Second Law

3.

Third Law

1.

First Law

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Analyzing Motion in a System Answers

AnalyzeGive examples of Newton’s laws in the system shown.

2.

Second Law

3.

Third Law

Acceleration increases as the
mass of the rocket decreases
from the spent fuel.

Thrust from the rocket causes
it to launch.

1.

First Law

Burning fuel pushes the rocket
forward while being pushed
out the back.

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Poll: Which of Newton’s Laws are Shown?

Analyze Discuss whether you can see evidence of each of
Newton’s three laws in the system in this image.

First Law

#

Second Law

#

Third Law

#

All of the above

#

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Exit Ticket

Choose one of the following ways to
describe a system in which all three of
Newton’s laws of motion are
demonstrated.

1.

Write a 7–8 sentence paragraph
about a system, citing how each law
is demonstrated.

2.

Draw and label a diagram of the
system so each law is highlighted.

Multiple Choice

Which of the following objects has the greatest inertia?

• A large truck parked in the side of the street

• A softball traveling at 95 miles per hour

• A laptop sitting on your desk

Multiple Choice

According to Newton's 2nd Law of Motion, force equals mass times ?

• inertia

• speed

• acceleration

• weight

Multiple Choice

When a water rocket pushes water out of the nozzle and the rocket is able to travel across the field - What # of Newton's Law is this?

• 1

• 2

• 3

Multiple Choice

A garbage can full of trash needs a stronger force to move it to the curb than an empty garbage can. Which of Newton's Laws does this represent?

• 1

• 2

• 3

Multiple Choice

Which part of the picture is the 'action' and the 'reaction'

• The action is the rocket lifting off and the reaction is the smoke coming out of the bottom

• The action is the smoke coming out of the bottom and the reaction is the rocket lifting off

Multiple Choice

Newton's third law states.......

• For each action there is a larger reaction associated with it.

• None of these choices

• For each action there is an equal and opposite reaction.

• For each action there is a smaller reaction associated with it.

Multiple Choice

A force of 40 N acts upon a 2 kg block. Calculate the acceleration of the object.

• 20 m/s²

• 20 m/s

• 80 m/s²

• 80 m/s

Multiple Choice

An object with a mass of 100 kg is observed to accelerate at the rate of 5 m/s2. Calculate the force required to produce this acceleration.

• 20N

• 500 M/S

• 500 Kg

• 500N

Multiple Choice

Newton's First Law States........

• Objects at rest tend to stay at rest unless acted on by an outside force.

• Objects accelerate often and it is difficult to know when or how they will accelerate.

• Objects in motion tend to stay in motion unless acted on by an outside force.

• Both A & C

Multiple Choice

If a 2kg bird is pushed by the wind with a force of 2N, how fast does the bird accelerate?

• 1 m
• 2 m/s²
• 4m/s²
• 1 m/s²

Multiple Choice

Football A has a greater mass than football B.  Which football will have greater acceleration when both are thrown with the same force in the same direction?

• Football A
• Football B
• They will have the same acceleration
• Mass has no effect on acceleration