Lesson 3 Reading Guide - Vocab

• inertia

• Newton’s first law of motion

• Newton’s second law of motion

• Newton’s third law of motion

• force pair

Newton’s Laws of Motion

Lesson 3-1

• A. Newton’s Laws• 1. Forces are measured in newtons (N).• 2. Isaac Newton studied the motion of

objects and summarized his findings in three laws

Newton’s Laws

Lesson 3-2• B. Newton’s First Law• 1. Inertia is the tendency of an object to

resist a change in its motion.

Newton’s First Law

inertiaScience Use the tendency to resist a change in motionCommon Use lack of action

Lesson 3-2

• 2. Newton’s first law of motion states that if the net force acting on an object is zero, the motion of the object doesnot change.

• 3. Sometimes Newton’s first law of motion is called the law of inertia.

Newton’s First Law (cont.)

Lesson 3-2

• 4. Newton’s first law explains the effect of balanced forces on an object.

• a. If balanced forces act on an object at rest, the object remains at rest.

• b. If balanced forces act on a moving object, the object continues to move at the same velocity.

Newton’s First Law (cont.)

• 5. The motion of an object changes only when a(n) net force acts on it according to Newton’s first law.

• a. Unbalanced forces can cause an object to accelerate, or speed up.

• b. They also can cause an object to decelerate, or slow down.

• c. They also can cause acceleration by causing the object to change direction.

Lesson 3-3• C. Newton’s Second Law of Motion• 1. Newton’s second law of motion states

that the acceleration of an object equals the force exerted on the object divided by the mass of the object.

Newton’s Second Law of Motion

Lesson 3-3

• 2. Newton’s second law explains the relationship among force, mass,and acceleration.

• Newton’s second law lets you predict what combination of force and mass you need to get the acceleration you need.

Newton’s Second Law of Motion (cont.)

Lesson 3-4• D. Newton’s Third Law• 1. Newton’s third law states that when

one object exerts a(n) force on a second object, the second object exerts a force of the same size but in the oppositedirection on the first object.

• a. The initial force is called the action force.

• b. The force exerted in response is called the reaction force.

Lesson 3-4

• 2. When two objects exert forces on each other, the two forces are a(n) force pair.

• a. Each force in a force pair acts on a(n) different object.

• b. Newton’s laws work together.

Newton’s Third Law (cont.)

Lesson 3-5

• E. Newton’s Laws in Action• 1. Newton’s laws do not apply to very

small objects, such as atoms.• 2. They also do not apply to objects

whose motion approaches the speed of light.

Newton’s Laws in Action

Lesson 3-5Newton’s Laws in Action (cont.)

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Masterfile

Lesson 3 - VS• Newton’s first law of motion states that

the motion of an object remains constant unless acted on by an outside force. This also is called the law of inertia.

Lesson 3 - VS• Newton’s second law of motion relates

an object’s acceleration to its mass and the net force applied to the object.

Lesson 3 - VS• Newton’s third law of motion states that

for every action force, there is an equal but opposite reaction force. The two forces are called a force pair.

Lesson 3 – LR1When balanced forces act on an object, the object is either moving with a constant velocity or _____.

A. speeding up

B. slowing down

C. changing direction

D. at rest

Lesson 3 – LR2

A. the direction of the action forceB. the direction of the inertiaC. the direction of the net forceD. the direction of reaction force

According to Newton’s second law of motion, the direction of acceleration is the same as which direction?

Lesson 3 – LR3

A. Newton’s first law of motion

B. Newton’s second law of motion

C. Newton’s third law of motion

D. a force pair

Which is also known as the law of inertia?

Lesson 3 - Now

5. All forces change the motion of objects.6. The net force on an object is equal to the

mass of the object times the acceleration of the object.

Do you agree or disagree?

Chapter Review Menu

Key Concept Summary

Interactive Concept Map

Chapter Review

Standardized Test Practice

The BIG IdeaForces are pushes and pulls that may change the motion of an object. Balanced forces result in an object remaining at rest or moving at a constant speed. Unbalanced forces result in the acceleration of an object.

Key Concepts 1• An object’s motion depends on how

it changes position. Motion can be described using speed, velocity, or acceleration.

• Speed is how fast an object moves. Velocity describes an object’s speed and the direction it moves. Acceleration describes the rate at which an object’s velocity changes.

• A graph can show you how either the displacement or the speed of an object changes over time.

Lesson 1: Describing Motion

Key Concepts 2Lesson 2: Forces

• A force is a push or pull on an object. Contact forces include friction and applied forces. Noncontact forces include gravity, electricity, and magnetism.

• Gravity is a force of attraction between any two objects. Gravitational force increases as the masses of the objects increase and decreases as the distance between the objects increases.

• Balanced forces acting on an object cause no change in the motion of the object. When unbalanced forces act on

an object, the sum of the forces is not equal to zero. Unbalanced forces cause acceleration.

Key Concepts 3• Inertia is the tendency of an object to resist a change of

motion Newton’s first law of motion states that an object will remain at rest or in constant straight-line motion unless unbalanced forces act on the object.

• Newton’s second law of motion states that the acceleration of an object increases as the force acting on it increases and decreases as the mass of the object increases.

• Newton’s third law of motion states that for every action force, there is an equal but opposite reaction force. The action-reaction forces are called a force pair.

Lesson 3: Newton’s Laws of Motion

Chapter Review – MC1

A. accelerationB. reference point C. speed D. velocity

To describe motion you need both direction and what?

Chapter Review – MC2

A. accelerationB. displacementC. speedD. velocity

Which describes the distance an object moves divided by the time it took to move that distance?

Chapter Review – MC3

A. contact forceB. frictionC. net forceD. noncontact force

Which term refers to a push or a pull applied by one object to another object that is touching it?

Chapter Review – MC4

A. frictionB. gravity C. inertiaD. mass

Which is a contact force that resists the sliding motion between two objects that are touching?

Chapter Review – MC5

A. force pairB. gravity C. inertia D. unbalanced forces

Which term describes the tendency of an object to resist a change in motion?

Chapter Review – STP1

A. inertiaB. massC. motionD. weight

Which changes when an unbalanced force acts on an object?

Chapter Review – STP2

A. acceleration B. displacementC. distanceD. velocity

Which is the speed and direction of an object’s motion?

Chapter Review – STP3

A. You pedal to speed up.B. You turn at constant speed. C. You coast to slow down. D. You pedal at constant speed.

You are riding a bike. In which situation are the forces acting on the bike balanced?

Chapter Review – STP4

A. frictionB. gravity C. inertiaD. net force

Which is a noncontact force that exists between all objects that have mass?

Chapter Review – STP5

A. action forceB. force pairC. inertia D. reaction force

When two objects exert forces on each other, the two forces are called what?