Transcript File
Slide 1
Chapter Introduction
Lesson 1
Gravity and Friction
Lesson 2
Newton’s
First Law
Lesson 3
Newton’s
Second Law
Lesson 4
Newton’s Third Law
Chapter Wrap-Up
Slide 2
How do forces
change the motion
of objects?
Slide 3
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
Slide 4
Do you agree or disagree?
1. You pull on objects around you with
the force of gravity.
2. Friction can act between two
unmoving, touching surfaces.
3. Forces acting on an object cannot be
added.
Slide 5
Do you agree or disagree?
4. A moving object will stop if no forces
act on it.
5. When an object’s speed increases,
the object accelerates.
6. If an object’s mass increases, its
acceleration also increases if the net
force acting on the object stays the
same.
Slide 6
Do you agree or disagree?
7. If objects collide, the object with
more mass applies more force.
8. Momentum is a measure of how
hard it is to stop a moving object.
Slide 7
Gravity and Friction
• What are some contact forces and
some noncontact forces?
• What is the law of universal
gravitation?
• How does friction affect the motion of
two objects sliding past each other?
Slide 8
Gravity and Friction
• force
• mass
• contact force
• weight
• noncontact force
• friction
• gravity
Slide 9
Types of Forces
• A push or a pull is called a force.
• An object or a person can apply a force
to another object or person.
force
from Latin fortis, means “strong”
Slide 10
Types of Forces (cont.)
• A contact force is a force that is applied
when two objects touch.
• A force that one object can apply to
another object without touching it is a
noncontact force.
• Gravity and magnetic force are
examples of noncontact forces.
Slide 11
Types of Forces (cont.)
What are some contact forces
and some noncontact forces?
Slide 12
What is gravity?
• Gravity is an attractive force that exists
between all objects that have mass.
• Objects fall to the ground because Earth
exerts gravity on them.
• Mass is the amount of matter in an
object.
• Mass is often measured in kilograms (kg).
Slide 13
• The SI unit for force is the newton (N).
• Arrows can be used to show both the
strength and direction of force.
Slide 14
What is gravity? (cont.)
• Sir Isaac Newton developed the law of
universal gravitation in the late 1600s.
• The law of universal gravitation states
that all objects are attracted to each
other by a gravitational force.
Slide 15
What is gravity? (cont.)
What is the law of universal
gravitation?
Slide 16
What is gravity? (cont.)
• The strength of force
depends on the mass
of each object and the
distance between them.
• When the mass of one
or both objects increases,
the gravitational force
between them also increases.
Slide 17
What is gravity? (cont.)
• Weight is the gravitational force exerted
on an object.
• Near Earth’s surface, an object’s weight
is the gravitational force exerted on the
object by Earth.
• Because weight is a force, it is measured
in newtons.
Slide 18
What is gravity? (cont.)
• An object’s weight is proportional to its
mass.
• Near Earth’s surface, the weight of an
object in newtons is about ten times its
mass in kilograms.
Slide 19
Friction
• Friction is a force that opposes the
movement between two touching
surfaces.
• There are several types of friction.
• static friction
• sliding friction
• fluid friction
Slide 20
Friction (cont.)
static
Science Use at rest or having no
motion
Common Use noise produced in a
radio or television
Slide 21
Friction (cont.)
• Static friction prevents surfaces from
sliding past each other.
• Up to a limit, the strength of static friction
changes to match the applied force.
• Sliding friction opposes the motion of
surfaces sliding past each other.
Slide 22
Friction (cont.)
• Fluid friction is friction between a surface
and a fluid—any material, such as water
or air, that flows.
• Fluid friction between a surface and air is
air resistance.
Slide 23
Friction (cont.)
• What causes friction between surfaces?
• When the microscopic dips and bumps
on one surface catch the dips and
bumps on another surface, the
microscopic roughness slows sliding.
• This is a source of friction.
Slide 24
Friction (cont.)
How does friction affect the
motion of two objects sliding
past each other?
Slide 25
Reducing Friction
Lubricants
decrease friction
and with less
friction, it is
easier for
surfaces to slide
past each other.
Slide 26
• Forces can be either contact, such as
a karate chop, or noncontact, such as
gravity. Each type is described by its
strength and direction.
Slide 27
• Gravity is an attractive force that acts
between any two objects that have
mass. The attraction is stronger for
objects with greater mass.
Slide 28
• Friction can reduce the speed of
objects sliding past each other. Air
resistance is a type of fluid friction that
slows the speed of a falling object.
Slide 29
Which refers to gravitational force
exerted on an object?
A. contact force
B. gravity
C. mass
D. weight
Slide 30
Which is proportional to an
object’s weight?
A. gravitational force
B. length
C. mass
D. noncontact force
Slide 31
Which is a force that opposes the
movement between two touching
surfaces?
A. net force
B. lubricant
C. gravity
D. friction
Slide 32
Do you agree or disagree?
1. You pull on objects around you with the
force of gravity.
2. Friction can act between two
unmoving, touching surfaces.
Slide 33
Newton’s First Law
• What is Newton’s first law of motion?
• How is motion related to balanced and
unbalanced forces?
• What effect does inertia have on the
motion of an object?
Slide 34
Newton’s First Law
• net force
• balanced forces
• unbalanced forces
• Newton’s first law of motion
• inertia
Slide 35
Identifying Forces
• The sum of all the forces acting on an
object is the net force.
• The net force depends on the directions
of the forces applied to an object.
• Because forces have direction, you have
to specify a reference direction when you
add forces.
Slide 36
Identifying Forces (cont.)
• A force moving in the reference direction
is positive, and a force in the opposite
direction is negative.
• When the forces applied to an object act
in the same direction, the net force is the
sum of the individual forces.
Slide 37
Identifying Forces (cont.)
• When forces act in opposite direction on
an object, the net force is still the sum of
the forces.
• The net force is the sum of the positive
and negative forces.
Slide 38
Identifying Forces (cont.)
• Balanced forces are forces that
combine and form a net force of zero.
• Forces that combine and form a net
force that is not zero are unbalanced
forces.
Slide 39
Newton’s First Law of Motion
• According to Newton’s first law of
motion, if the net force on an object is
zero, an object at rest will stay at rest,
and a moving object will continue moving
in a straight line with constant speed.
• As a result, balanced forces and
unbalanced forces have different results
when they act on an object.
Slide 40
Newton’s First Law of Motion (cont.)
What is Newton’s first law
of motion?
Slide 41
Newton’s First Law of Motion (cont.)
• Balanced forces acting on an object do
not change the object’s speed and
direction.
• Newton’s first law of motion only applies
to balanced forces acting on an object.
• When unbalanced forces act on an
object, the object’s velocity changes.
Slide 42
Newton’s First Law of Motion (cont.)
How is motion related to balanced
and unbalanced forces?
Slide 43
Newton’s First Law of Motion (cont.)
The tendency of an object to resist a
change in its motion is called inertia.
inertia
from Latin iners, means “without
skill, inactive”
Slide 44
Newton’s First Law of Motion (cont.)
What effect does inertial have on
the motion of an object?
Slide 45
Why do objects stop moving?
• For an object to start moving, a force
greater than static friction must be
applied to it.
• To keep an object in motion, a force at
least as strong as friction must be
applied continuously.
• Objects stop moving because friction or
another force acts on them.
Slide 46
• Unbalanced forces cause an object
to move.
• According to Newton’s first law of
motion, if the net force on an object
is zero, the object’s velocity does not
change.
• Inertia is a property that resists a
change in the motion of an object.
Slide 47
Which refers to forces that
combine and form a net force that
is not zero?
A. balanced forces
B. inertia
C. net force
D. unbalanced forces
Slide 48
Which could cause an object to
stop moving?
A. friction
B. inertia
C. unbalanced forces
D. velocity
Slide 49
When equal forces act on an object
in opposite directions, what is the
net force on the object?
A. zero
B. one
C. equal
D. balanced
Slide 50
Do you agree or disagree?
3. Forces acting on an object cannot be
added.
4. A moving object will stop if no forces
act on it.
Slide 51
Newton’s Second Law
• What is Newton’s second law of
motion?
• How does centripetal force affect
circular motion?
Slide 52
Newton’s Second Law
• Newton’s second law of motion
• circular motion
• centripetal force
Slide 53
How do forces change motion?
• Forces change an object’s motion by
changing its speed, its direction, or both
its speed and its direction.
• Velocity is speed in a certain direction.
• Only unbalanced forces change an
object’s velocity.
Slide 54
How do forces change motion? (cont.)
• When unbalanced forces act on an
object at rest, the object begins moving
in the direction of the net force.
• If the net force acting on a moving object
is in the direction that the object is
moving, the object will speed up.
• If the direction of the net force on an
object is opposite to the direction the
object moves, the object slows down.
Slide 55
When unbalanced forces act on a ball at
rest, it moves in the direction of the net
force.
Slide 56
How do forces change motion? (cont.)
• Unbalanced forces can change an
object’s velocity by changing the object’s
direction.
• Another name for a change in velocity
over time is acceleration.
• Unbalanced forces make an object
accelerate by changing its speed, its
direction, or both.
Slide 57
Newton’s Second Law of Motion
According to Newton’s second law of
motion, the acceleration of an object is
equal to the net force acting on the object
divided by the object’s mass.
Slide 58
Slide 59
Newton’s Second Law of Motion (cont.)
• The direction of acceleration is the same
as the direction of the net force.
• Acceleration is expressed in meters per
second squared (m/s2), mass in
kilograms (kg), and force in newtons (N).
Slide 60
Circular Motion
• Circular motion is any motion in which
an object is moving along a curved path.
• In circular motion, a force that acts
perpendicular to the direction of motion,
toward the center of the curve, is
centripetal force.
Slide 61
Circular Motion (cont.)
centripetal
from Latin centripetus, means
“toward the center”
Slide 62
Circular Motion (cont.)
Slide 63
Circular Motion (cont.)
How does centripetal force affect
circular motion?
Slide 64
Circular Motion (cont.)
• A satellite is an object that orbits a larger
object.
• A satellite tends to move along a straight
path because of inertia.
• Gravity is the centripetal force that keeps
a satellite in orbit by changing its
direction.
Slide 65
• Unbalanced
forces cause an
object to speed
up, slow down,
or change
direction.
Slide 66
• Newton’s
second law of
motion relates
an objects
acceleration
to its mass and
the net force on
the object.
Slide 67
• Any motion in
which an object
is moving along
a curved path is
circular motion.
Slide 68
Which term refers to speed in a
certain direction?
A. acceleration
B. centripetal force
C. inertia
D. velocity
Slide 69
Which refers to motion along a
curved path?
A. acceleration
B. centripetal
C. circular
D. unbalanced
Slide 70
Which refers to a change in
velocity over time?
A. inertia
B. acceleration
C. circulation motion
D. centripetal force
Slide 71
Do you agree or disagree?
5. When an object’s speed increases,
the object accelerates.
6. If an object’s mass increases, its
acceleration also increases if the net
force acting on the object stays the
same.
Slide 72
Newton’s Third Law
• What is Newton’s third law of motion?
• Why don’t the forces in a force pair
cancel each other?
• What is the law of conservation of
momentum?
Slide 73
Newton’s Third Law
• Newton’s third law of motion
• force pair
• momentum
• law of conservation of momentum
Slide 74
Opposite Forces
When an object applies a force on another
object, the second object applies a force of
the same strength on the first object, but
the force is in the opposite direction.
Slide 75
Newton’s Third Law of Motion
According to Newton’s third law of
motion, when one object applies a force
on a second object, the second object
applies an equal force in the opposite
direction on the first object.
What is Newton’s third law
of motion?
Slide 76
Newton’s Third Law of Motion (cont.)
• A force pair is the forces two objects
apply to each other.
• If the forces of a force pair always act in
opposite directions and are always the
same strength, they do not cancel each
other out because each force acts on a
different object.
Slide 77
Newton’s Third Law of Motion (cont.)
• Adding forces can only result in a net
force of zero if the forces act on the
same object.
• In a force pair, one force is called the
action force and the other force is called
the reaction force.
Slide 78
Newton’s Third Law of Motion (cont.)
Why don’t the forces in a force
pair cancel each other?
Slide 79
Using Newton’s Third Law of Motion
• When you push against an object, the
force you apply is called the action force.
• The force applied by the object back
against you is called the reaction force.
• According to Newton’s third law of
motion, every action force has a reaction
force in the opposite direction.
Slide 80
Momentum
Momentum is a measure of how hard it is
to stop a moving object.
momentum
from Latin momentum, means
“movement, impulse”
Slide 81
Momentum (cont.)
Momentum is the product of an object’s
mass and velocity.
Slide 82
Slide 83
Momentum (cont.)
• An object’s momentum is in the same
direction as its velocity.
• According to Newton’s first law, if the net
force on an object is zero, neither its
velocity nor its momentum change.
• Because momentum is the product of
mass and velocity, the force on an object
equals its change in momentum.
Slide 84
Conservation of Momentum
According to the law of conservation of
momentum, the total momentum of a group
of objects stays the same unless outside
forces such as friction act on the objects.
What is the law of conservation
of momentum?
Slide 85
Conservation of Momentum (cont.)
• When colliding objects bounce off each
other, it is an elastic collision.
• If objects collide and stick together, the
collision is inelastic.
• No matter the type of collision, the total
momentum will be the same before and
after the collision.
Slide 86
• Newton’s third law of motion
describes the force pair between two
objects.
• For every action force, there is a
reaction force that is equal in
strength but opposite in direction.
• In any collision, momentum is
transferred from one object to
another.
Slide 87
Which law explains that every
force has a reaction force in the
opposite direction?
A. Newton’s third law of motion
B. Newton’s second law of motion
C. Newton’s first law of motion
D. law of conservation of momentum
Slide 88
Which is a measure of how hard it
is to stop a moving object?
A. velocity
B. momentum
C. inertia
D. elastic collision
Slide 89
Which refers to the forces two
objects apply to each other?
A. velocity
B. momentum
C. force pair
D. collision
Slide 90
Do you agree or disagree?
7. If objects collide, the object with more
mass applies more force.
8. Momentum is a measure of how hard it
is to stop a moving object.
Slide 91
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Slide 92
An object’s motion
changes if a net force
acts on the object.
Slide 93
Lesson 1: Gravity and Friction
• Friction is a contact force. Magnetism is a
noncontact force.
• The law of universal gravitation states that all
objects are attracted to each other by gravity.
• Friction can stop or slow down objects sliding past
each other.
Slide 94
Lesson 2: Newton’s First Law
• An object’s motion can only be changed by
unbalanced forces.
• According to Newton’s first law of motion, the motion
of an object is not changed by balanced forces
acting on it.
• Inertia is the tendency of an object to resist a
change in its motion.
Slide 95
Lesson 3: Newton’s Second Law
• According to Newton’s second law of motion, an
object’s acceleration is the net force on the object
divided by its mass.
• In circular motion, a centripetal force pulls an object
toward the center of the curve.
Slide 96
Lesson 4: Newton’s Third Law
• Newton’s third law of motion states that when one
object applies a force on another, the second object
applies an equal force in the opposite direction on
the first object.
• The forces of a force pair do not cancel because
they act on different objects.
• According to the law of conservation of momentum,
momentum is conserved during a collision unless an
outside force acts on the colliding objects.
Slide 97
Which term refers to the amount
of matter in an object?
A. weight
B. mass
C. inertia
D. gravity
Slide 98
Which refers to a force that is
applied when two objects touch?
A. contact
B. gravity
C. mass
D. noncontact
Slide 99
Which term refers to forces that
combine with a net force of zero?
A. unbalanced
B. terminal
C. centripetal
D. balanced
Slide 100
The tendency of an object to
resist a change in its motion is
called what?
A. velocity
B. terminal velocity
C. net force
D. inertia
Slide 101
Which law states that the total
momentum of a group of objects
stays the same unless outside
forces act on the objects?
A. Newton’s third law of motion
B. Newton’s second law of motion
C. Newton’s first law of motion
D. law of conservation of momentum
Slide 102
Which term refers to a force that
one object can apply to another
without touching?
A. weight
B. noncontact
C. inertia
D. contact
Slide 103
Which describes the magnetic
force?
A. contact
B. gravitational
C. noncontact
D. static
Slide 104
Which describes the net force
of different forces acting in the
same direction?
A. unbalanced
B. proportional
C. noncontact
D. negative
Slide 105
If the net force acting on a moving
object is in the direction that the
object is moving, the object does
what?
A. stops
B. speeds up
C. slows down
D. changes direction
Slide 106
Which refers to the collision of
objects that bounce off each
other?
A. elastic
B. friction
C. inelastic
D. inertia
Chapter Introduction
Lesson 1
Gravity and Friction
Lesson 2
Newton’s
First Law
Lesson 3
Newton’s
Second Law
Lesson 4
Newton’s Third Law
Chapter Wrap-Up
Slide 2
How do forces
change the motion
of objects?
Slide 3
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
Slide 4
Do you agree or disagree?
1. You pull on objects around you with
the force of gravity.
2. Friction can act between two
unmoving, touching surfaces.
3. Forces acting on an object cannot be
added.
Slide 5
Do you agree or disagree?
4. A moving object will stop if no forces
act on it.
5. When an object’s speed increases,
the object accelerates.
6. If an object’s mass increases, its
acceleration also increases if the net
force acting on the object stays the
same.
Slide 6
Do you agree or disagree?
7. If objects collide, the object with
more mass applies more force.
8. Momentum is a measure of how
hard it is to stop a moving object.
Slide 7
Gravity and Friction
• What are some contact forces and
some noncontact forces?
• What is the law of universal
gravitation?
• How does friction affect the motion of
two objects sliding past each other?
Slide 8
Gravity and Friction
• force
• mass
• contact force
• weight
• noncontact force
• friction
• gravity
Slide 9
Types of Forces
• A push or a pull is called a force.
• An object or a person can apply a force
to another object or person.
force
from Latin fortis, means “strong”
Slide 10
Types of Forces (cont.)
• A contact force is a force that is applied
when two objects touch.
• A force that one object can apply to
another object without touching it is a
noncontact force.
• Gravity and magnetic force are
examples of noncontact forces.
Slide 11
Types of Forces (cont.)
What are some contact forces
and some noncontact forces?
Slide 12
What is gravity?
• Gravity is an attractive force that exists
between all objects that have mass.
• Objects fall to the ground because Earth
exerts gravity on them.
• Mass is the amount of matter in an
object.
• Mass is often measured in kilograms (kg).
Slide 13
• The SI unit for force is the newton (N).
• Arrows can be used to show both the
strength and direction of force.
Slide 14
What is gravity? (cont.)
• Sir Isaac Newton developed the law of
universal gravitation in the late 1600s.
• The law of universal gravitation states
that all objects are attracted to each
other by a gravitational force.
Slide 15
What is gravity? (cont.)
What is the law of universal
gravitation?
Slide 16
What is gravity? (cont.)
• The strength of force
depends on the mass
of each object and the
distance between them.
• When the mass of one
or both objects increases,
the gravitational force
between them also increases.
Slide 17
What is gravity? (cont.)
• Weight is the gravitational force exerted
on an object.
• Near Earth’s surface, an object’s weight
is the gravitational force exerted on the
object by Earth.
• Because weight is a force, it is measured
in newtons.
Slide 18
What is gravity? (cont.)
• An object’s weight is proportional to its
mass.
• Near Earth’s surface, the weight of an
object in newtons is about ten times its
mass in kilograms.
Slide 19
Friction
• Friction is a force that opposes the
movement between two touching
surfaces.
• There are several types of friction.
• static friction
• sliding friction
• fluid friction
Slide 20
Friction (cont.)
static
Science Use at rest or having no
motion
Common Use noise produced in a
radio or television
Slide 21
Friction (cont.)
• Static friction prevents surfaces from
sliding past each other.
• Up to a limit, the strength of static friction
changes to match the applied force.
• Sliding friction opposes the motion of
surfaces sliding past each other.
Slide 22
Friction (cont.)
• Fluid friction is friction between a surface
and a fluid—any material, such as water
or air, that flows.
• Fluid friction between a surface and air is
air resistance.
Slide 23
Friction (cont.)
• What causes friction between surfaces?
• When the microscopic dips and bumps
on one surface catch the dips and
bumps on another surface, the
microscopic roughness slows sliding.
• This is a source of friction.
Slide 24
Friction (cont.)
How does friction affect the
motion of two objects sliding
past each other?
Slide 25
Reducing Friction
Lubricants
decrease friction
and with less
friction, it is
easier for
surfaces to slide
past each other.
Slide 26
• Forces can be either contact, such as
a karate chop, or noncontact, such as
gravity. Each type is described by its
strength and direction.
Slide 27
• Gravity is an attractive force that acts
between any two objects that have
mass. The attraction is stronger for
objects with greater mass.
Slide 28
• Friction can reduce the speed of
objects sliding past each other. Air
resistance is a type of fluid friction that
slows the speed of a falling object.
Slide 29
Which refers to gravitational force
exerted on an object?
A. contact force
B. gravity
C. mass
D. weight
Slide 30
Which is proportional to an
object’s weight?
A. gravitational force
B. length
C. mass
D. noncontact force
Slide 31
Which is a force that opposes the
movement between two touching
surfaces?
A. net force
B. lubricant
C. gravity
D. friction
Slide 32
Do you agree or disagree?
1. You pull on objects around you with the
force of gravity.
2. Friction can act between two
unmoving, touching surfaces.
Slide 33
Newton’s First Law
• What is Newton’s first law of motion?
• How is motion related to balanced and
unbalanced forces?
• What effect does inertia have on the
motion of an object?
Slide 34
Newton’s First Law
• net force
• balanced forces
• unbalanced forces
• Newton’s first law of motion
• inertia
Slide 35
Identifying Forces
• The sum of all the forces acting on an
object is the net force.
• The net force depends on the directions
of the forces applied to an object.
• Because forces have direction, you have
to specify a reference direction when you
add forces.
Slide 36
Identifying Forces (cont.)
• A force moving in the reference direction
is positive, and a force in the opposite
direction is negative.
• When the forces applied to an object act
in the same direction, the net force is the
sum of the individual forces.
Slide 37
Identifying Forces (cont.)
• When forces act in opposite direction on
an object, the net force is still the sum of
the forces.
• The net force is the sum of the positive
and negative forces.
Slide 38
Identifying Forces (cont.)
• Balanced forces are forces that
combine and form a net force of zero.
• Forces that combine and form a net
force that is not zero are unbalanced
forces.
Slide 39
Newton’s First Law of Motion
• According to Newton’s first law of
motion, if the net force on an object is
zero, an object at rest will stay at rest,
and a moving object will continue moving
in a straight line with constant speed.
• As a result, balanced forces and
unbalanced forces have different results
when they act on an object.
Slide 40
Newton’s First Law of Motion (cont.)
What is Newton’s first law
of motion?
Slide 41
Newton’s First Law of Motion (cont.)
• Balanced forces acting on an object do
not change the object’s speed and
direction.
• Newton’s first law of motion only applies
to balanced forces acting on an object.
• When unbalanced forces act on an
object, the object’s velocity changes.
Slide 42
Newton’s First Law of Motion (cont.)
How is motion related to balanced
and unbalanced forces?
Slide 43
Newton’s First Law of Motion (cont.)
The tendency of an object to resist a
change in its motion is called inertia.
inertia
from Latin iners, means “without
skill, inactive”
Slide 44
Newton’s First Law of Motion (cont.)
What effect does inertial have on
the motion of an object?
Slide 45
Why do objects stop moving?
• For an object to start moving, a force
greater than static friction must be
applied to it.
• To keep an object in motion, a force at
least as strong as friction must be
applied continuously.
• Objects stop moving because friction or
another force acts on them.
Slide 46
• Unbalanced forces cause an object
to move.
• According to Newton’s first law of
motion, if the net force on an object
is zero, the object’s velocity does not
change.
• Inertia is a property that resists a
change in the motion of an object.
Slide 47
Which refers to forces that
combine and form a net force that
is not zero?
A. balanced forces
B. inertia
C. net force
D. unbalanced forces
Slide 48
Which could cause an object to
stop moving?
A. friction
B. inertia
C. unbalanced forces
D. velocity
Slide 49
When equal forces act on an object
in opposite directions, what is the
net force on the object?
A. zero
B. one
C. equal
D. balanced
Slide 50
Do you agree or disagree?
3. Forces acting on an object cannot be
added.
4. A moving object will stop if no forces
act on it.
Slide 51
Newton’s Second Law
• What is Newton’s second law of
motion?
• How does centripetal force affect
circular motion?
Slide 52
Newton’s Second Law
• Newton’s second law of motion
• circular motion
• centripetal force
Slide 53
How do forces change motion?
• Forces change an object’s motion by
changing its speed, its direction, or both
its speed and its direction.
• Velocity is speed in a certain direction.
• Only unbalanced forces change an
object’s velocity.
Slide 54
How do forces change motion? (cont.)
• When unbalanced forces act on an
object at rest, the object begins moving
in the direction of the net force.
• If the net force acting on a moving object
is in the direction that the object is
moving, the object will speed up.
• If the direction of the net force on an
object is opposite to the direction the
object moves, the object slows down.
Slide 55
When unbalanced forces act on a ball at
rest, it moves in the direction of the net
force.
Slide 56
How do forces change motion? (cont.)
• Unbalanced forces can change an
object’s velocity by changing the object’s
direction.
• Another name for a change in velocity
over time is acceleration.
• Unbalanced forces make an object
accelerate by changing its speed, its
direction, or both.
Slide 57
Newton’s Second Law of Motion
According to Newton’s second law of
motion, the acceleration of an object is
equal to the net force acting on the object
divided by the object’s mass.
Slide 58
Slide 59
Newton’s Second Law of Motion (cont.)
• The direction of acceleration is the same
as the direction of the net force.
• Acceleration is expressed in meters per
second squared (m/s2), mass in
kilograms (kg), and force in newtons (N).
Slide 60
Circular Motion
• Circular motion is any motion in which
an object is moving along a curved path.
• In circular motion, a force that acts
perpendicular to the direction of motion,
toward the center of the curve, is
centripetal force.
Slide 61
Circular Motion (cont.)
centripetal
from Latin centripetus, means
“toward the center”
Slide 62
Circular Motion (cont.)
Slide 63
Circular Motion (cont.)
How does centripetal force affect
circular motion?
Slide 64
Circular Motion (cont.)
• A satellite is an object that orbits a larger
object.
• A satellite tends to move along a straight
path because of inertia.
• Gravity is the centripetal force that keeps
a satellite in orbit by changing its
direction.
Slide 65
• Unbalanced
forces cause an
object to speed
up, slow down,
or change
direction.
Slide 66
• Newton’s
second law of
motion relates
an objects
acceleration
to its mass and
the net force on
the object.
Slide 67
• Any motion in
which an object
is moving along
a curved path is
circular motion.
Slide 68
Which term refers to speed in a
certain direction?
A. acceleration
B. centripetal force
C. inertia
D. velocity
Slide 69
Which refers to motion along a
curved path?
A. acceleration
B. centripetal
C. circular
D. unbalanced
Slide 70
Which refers to a change in
velocity over time?
A. inertia
B. acceleration
C. circulation motion
D. centripetal force
Slide 71
Do you agree or disagree?
5. When an object’s speed increases,
the object accelerates.
6. If an object’s mass increases, its
acceleration also increases if the net
force acting on the object stays the
same.
Slide 72
Newton’s Third Law
• What is Newton’s third law of motion?
• Why don’t the forces in a force pair
cancel each other?
• What is the law of conservation of
momentum?
Slide 73
Newton’s Third Law
• Newton’s third law of motion
• force pair
• momentum
• law of conservation of momentum
Slide 74
Opposite Forces
When an object applies a force on another
object, the second object applies a force of
the same strength on the first object, but
the force is in the opposite direction.
Slide 75
Newton’s Third Law of Motion
According to Newton’s third law of
motion, when one object applies a force
on a second object, the second object
applies an equal force in the opposite
direction on the first object.
What is Newton’s third law
of motion?
Slide 76
Newton’s Third Law of Motion (cont.)
• A force pair is the forces two objects
apply to each other.
• If the forces of a force pair always act in
opposite directions and are always the
same strength, they do not cancel each
other out because each force acts on a
different object.
Slide 77
Newton’s Third Law of Motion (cont.)
• Adding forces can only result in a net
force of zero if the forces act on the
same object.
• In a force pair, one force is called the
action force and the other force is called
the reaction force.
Slide 78
Newton’s Third Law of Motion (cont.)
Why don’t the forces in a force
pair cancel each other?
Slide 79
Using Newton’s Third Law of Motion
• When you push against an object, the
force you apply is called the action force.
• The force applied by the object back
against you is called the reaction force.
• According to Newton’s third law of
motion, every action force has a reaction
force in the opposite direction.
Slide 80
Momentum
Momentum is a measure of how hard it is
to stop a moving object.
momentum
from Latin momentum, means
“movement, impulse”
Slide 81
Momentum (cont.)
Momentum is the product of an object’s
mass and velocity.
Slide 82
Slide 83
Momentum (cont.)
• An object’s momentum is in the same
direction as its velocity.
• According to Newton’s first law, if the net
force on an object is zero, neither its
velocity nor its momentum change.
• Because momentum is the product of
mass and velocity, the force on an object
equals its change in momentum.
Slide 84
Conservation of Momentum
According to the law of conservation of
momentum, the total momentum of a group
of objects stays the same unless outside
forces such as friction act on the objects.
What is the law of conservation
of momentum?
Slide 85
Conservation of Momentum (cont.)
• When colliding objects bounce off each
other, it is an elastic collision.
• If objects collide and stick together, the
collision is inelastic.
• No matter the type of collision, the total
momentum will be the same before and
after the collision.
Slide 86
• Newton’s third law of motion
describes the force pair between two
objects.
• For every action force, there is a
reaction force that is equal in
strength but opposite in direction.
• In any collision, momentum is
transferred from one object to
another.
Slide 87
Which law explains that every
force has a reaction force in the
opposite direction?
A. Newton’s third law of motion
B. Newton’s second law of motion
C. Newton’s first law of motion
D. law of conservation of momentum
Slide 88
Which is a measure of how hard it
is to stop a moving object?
A. velocity
B. momentum
C. inertia
D. elastic collision
Slide 89
Which refers to the forces two
objects apply to each other?
A. velocity
B. momentum
C. force pair
D. collision
Slide 90
Do you agree or disagree?
7. If objects collide, the object with more
mass applies more force.
8. Momentum is a measure of how hard it
is to stop a moving object.
Slide 91
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Slide 92
An object’s motion
changes if a net force
acts on the object.
Slide 93
Lesson 1: Gravity and Friction
• Friction is a contact force. Magnetism is a
noncontact force.
• The law of universal gravitation states that all
objects are attracted to each other by gravity.
• Friction can stop or slow down objects sliding past
each other.
Slide 94
Lesson 2: Newton’s First Law
• An object’s motion can only be changed by
unbalanced forces.
• According to Newton’s first law of motion, the motion
of an object is not changed by balanced forces
acting on it.
• Inertia is the tendency of an object to resist a
change in its motion.
Slide 95
Lesson 3: Newton’s Second Law
• According to Newton’s second law of motion, an
object’s acceleration is the net force on the object
divided by its mass.
• In circular motion, a centripetal force pulls an object
toward the center of the curve.
Slide 96
Lesson 4: Newton’s Third Law
• Newton’s third law of motion states that when one
object applies a force on another, the second object
applies an equal force in the opposite direction on
the first object.
• The forces of a force pair do not cancel because
they act on different objects.
• According to the law of conservation of momentum,
momentum is conserved during a collision unless an
outside force acts on the colliding objects.
Slide 97
Which term refers to the amount
of matter in an object?
A. weight
B. mass
C. inertia
D. gravity
Slide 98
Which refers to a force that is
applied when two objects touch?
A. contact
B. gravity
C. mass
D. noncontact
Slide 99
Which term refers to forces that
combine with a net force of zero?
A. unbalanced
B. terminal
C. centripetal
D. balanced
Slide 100
The tendency of an object to
resist a change in its motion is
called what?
A. velocity
B. terminal velocity
C. net force
D. inertia
Slide 101
Which law states that the total
momentum of a group of objects
stays the same unless outside
forces act on the objects?
A. Newton’s third law of motion
B. Newton’s second law of motion
C. Newton’s first law of motion
D. law of conservation of momentum
Slide 102
Which term refers to a force that
one object can apply to another
without touching?
A. weight
B. noncontact
C. inertia
D. contact
Slide 103
Which describes the magnetic
force?
A. contact
B. gravitational
C. noncontact
D. static
Slide 104
Which describes the net force
of different forces acting in the
same direction?
A. unbalanced
B. proportional
C. noncontact
D. negative
Slide 105
If the net force acting on a moving
object is in the direction that the
object is moving, the object does
what?
A. stops
B. speeds up
C. slows down
D. changes direction
Slide 106
Which refers to the collision of
objects that bounce off each
other?
A. elastic
B. friction
C. inelastic
D. inertia