1. Lesson 3 Reading Guide - Vocab
Newton’s Laws of Motion
inertia
Newton’s first law of motion
Newton’s second law of motion
Newton’s third law of motion
force pair

2. Lesson 3-1 Newton’s Laws 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

3. Lesson 3-2 Newton’s First Law B. Newton’s First Law
1. Inertia is the tendency of an object to resist a change in its motion.
inertia
Science Use the tendency to resist a change in motion
Common Use lack of action

4. Lesson 3-2 Newton’s First Law (cont.)
2. Newton’s first law of motion states that if the net force acting on an object is zero, the motion of the object does not change.
3. Sometimes Newton’s first law of motion is called the law of inertia.

5. Lesson 3-2 Newton’s First Law (cont.)
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.

6. 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.

7. Lesson 3-3 Newton’s Second Law of Motion
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.

8. Lesson 3-3 Newton’s Second Law of Motion (cont.)
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.

9. 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 opposite direction on the first object.
a. The initial force is called the action force.
b. The force exerted in response is called the reaction force.

10. Lesson 3-4 Newton’s Third Law (cont.)
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.

11. Lesson 3-5 Newton’s Laws in Action 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.

12. Lesson 3-5 Newton’s Laws in Action (cont.) DEX IMAGE/Getty Images
Masterfile

13. 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.

14. 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.

15. 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.

16. Lesson 3 – LR1
When 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

17. Lesson 3 – LR2
According to Newton’s second law of motion, the direction of acceleration is the same as which direction?
A. the direction of the action force
B. the direction of the inertia
C. the direction of the net force
D. the direction of reaction force

18. Lesson 3 – LR3 Which is also known as the law of inertia?
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

19. Lesson 3 - Now 5. All forces change the motion of objects.
Do you agree or disagree?
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.

20. Chapter Review Menu Key Concept Summary Interactive Concept Map
Standardized Test Practice

21. The BIG Idea
Forces 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.

22. Key Concepts 1
Lesson 1: Describing Motion
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.

23. Key Concepts 2
Lesson 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.

24. Key Concepts 3
Lesson 3: Newton’s Laws of Motion
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.

25. Chapter Review – MC1
To describe motion you need both direction and what?
A. acceleration
B. reference point
C. speed
D. velocity

26. Chapter Review – MC2
Which describes the distance an object moves divided by the time it took to move that distance?
A. acceleration
B. displacement
C. speed
D. velocity

27. Chapter Review – MC3
Which term refers to a push or a pull applied by one object to another object that is touching it?
A. contact force
B. friction
C. net force
D. noncontact force

28. Chapter Review – MC4
Which is a contact force that resists the sliding motion between two objects that are touching?
A. friction
B. gravity
C. inertia
D. mass

29. Chapter Review – MC5
Which term describes the tendency of an object to resist a change in motion?
A. force pair
B. gravity
C. inertia
D. unbalanced forces

30. Chapter Review – STP1
Which changes when an unbalanced force acts on an object?
A. inertia
B. mass
C. motion
D. weight

31. Chapter Review – STP2
Which is the speed and direction of an object’s motion?
A. acceleration
B. displacement
C. distance
D. velocity

32. Chapter Review – STP3
You are riding a bike. In which situation are the forces acting on the bike balanced?
A. You pedal to speed up.
B. You turn at constant speed.
C. You coast to slow down.
D. You pedal at constant speed.

33. Chapter Review – STP4
Which is a noncontact force that exists between all objects that have mass?
A. friction
B. gravity
C. inertia
D. net force

34. Chapter Review – STP5
When two objects exert forces on each other, the two forces are called what?
A. action force
B. force pair
C. inertia
D. reaction force