1. Newton’s 3 Laws of Motion
Unit 8
Section 2

2. Newton’s 1st Law
a. “An object at rest remains at rest, and an object in motion stays in motion, unless acted on by an unbalanced force.”

3. What Does This Mean?
b. If something is moving it will keep moving unless something stops it.
c. It also means that if something is just sitting there, it will just keep sitting there unless something moves it.
Simple as that!

6. Law of Inertia
d. Sometimes Newton’s 1st Law of Motion is called the Law of Inertia.
e. Inertia is “the tendency of an object to resist being moved, or if the object is moving, to resist a change in speed or direction until an outside force acts on it.”
f. Basically, all objects just want to keep doing whatever they are doing.

7. What Sort of Forces Act on an Object to Make it Move or Stop?
g. Examples of forces acting on an object.
Friction
Unbalanced forces
Air resistance
Gravity
Push/pull

8. A Video to Make you think.
Newton’s First Law of Motion Video

9. Newton’s 2nd Law of Motion
a. “The acceleration of an object depends on the mass of the object and the amount of force applied.”

10. What Does This Mean?
b. It means that if something has a lot of mass, you have to exert more force to move or stop it. (More mass= more force to move or stop it.)
c. If something has less mass, less force is needed to move or stop it. (Less mass= less force to move or stop it.)
d. Newton’s 2nd Law is
Force=mass x acceleration or F=m x a

11. Shopping Cart Example
e. This means that “the acceleration of an object decreases as its mass increases.”
When you push an empty shopping cart, you hardly have to exert any force to move it. But once you put food in it, you have to exert more force to make it move.
Harder
Acceleration Decreases
More Mass
Easy
Acceleration Increases
Less Mass

12. Think About It…… Which will take more force to accelerate?
The bowling ball or a bouncy ball?

13. Newton’s 3rd Law of Motion
a. “Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.”

14. What Does This Mean?
b. For every action, there is an equal and opposite reaction.
c. Examples of Newton’s 3rd Law
1. A rocket ship launching. The gases push down and the rocket moves up.
2. Blowing up a balloon and letting it go. The air pushes towards you and the balloon flies away from you.
d. All forces act in force pairs.
e. Example:
1. If I hit a ball, the ball will go flying.
force pair - (ball and bat)
2. If I blow up a balloon and let it go.
force pair - (air pushing out and balloon)
f. If a rocket blasts exhaust gases downward the gases will push the shuttle upward with an equal force.
Click here for Example.

15. Force Pairs
If I blow up a balloon and let it go, what are the force pairs?
Where will the balloon go?
Newton’s Third Law of Motion Video

16. Quickie Quiz
Which law: An object at rest will remain at rest, and an object in motion will remain in motion unless acted on by an outside force.
1st
2nd
3rd

17. Quickie Quiz
Which law: For every action there is an equal and opposite reaction.
1st
2nd
3rd

18. Quickie Quiz
The tendency of an object to keep doing whatever it is doing is known as:
Gravity
Acceleration
Inertia

19. Quickie Quiz
Which law: F = ma
1st
2nd
3rd

20. Videos to Make you think.
Newton’s First Law of Motion Video
Newton’s Second Law of Motion Video
Newton’s Third Law of Motion Video