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 outside (unbalanced) force.”

3. What Does This Mean?
b. This means that 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. II. Examples of Newton’s First Law
A rolling ball comes to a stop due to friction.
a. The ball is the object in motion and the outside force is friction that makes it come to rest.
Seatbelts
a. If you brake while driving your car, your body is an object in motion and you would keep moving forward if it wasn’t for your seatbelt (outside force) that makes you come to rest.
3. Riding your bicycle than braking.
a. The bike is the object in motion and the brake is the outside force that makes you come to rest.

7. III. Law of Inertia
a. Sometimes Newton’s 1st Law of Motion is called the Law of Inertia.
b. 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.”
i. Basically, all objects just want to keep doing whatever they are doing.

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

9. 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

10. 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.”

11. What Does This Mean? b. More mass= more force to move or stop it.
c. Less mass= less force to move or stop it.
d. The formulas for Newton’s 2nd Law are
Force=mass x acceleration or F=m x a

12. Shopping Cart Example
e. This means that the acceleration of an object decreases as its mass increases.
Harder
Acceleration Decreases
More Mass
Easy
Acceleration Increases
Less Mass

13. V. Examples of Newton’s 2nd Law
Pushing an empty shopping cart compared to a full shopping cart.
a. 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.
2. Pushing your little sister on a swing comparted to pushing your dad on a swing.
Your little sitter requires less force to make her accelerate because she has a small mass and your father requires more force to make him accelerate.

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

15. Newton’s 3rd Law
Whenever one object exerts a force on another object the second object exerts an equal and opposite force on the first.
Shortened version: “For every action, there’s an equal and opposite reaction.”

16. What Does This Mean? c. Examples of Newton’s 3rd Law
1. A space ship launching.
a. The gases push down and the rocket moves up.
2. Blowing up a balloon and letting it go.
a. The air pushes towards you and the balloon
flies away from you.
d. All forces act as force pairs.
e. Force pairs-are when there’s an action (what comes first) and a reaction (what comes after)
f. If a rocket blasts exhaust gases downward (action) the gases will push the shuttle upward (reaction) with an equal force.

17. g. Examples of Force Pairs:
1. If I hit a ball, the ball will go flying.
force pair - (ball and bat)
action- hit the ball reaction- ball goes flying
2. If I blow up a balloon and let it go.
force pair - (air and balloon)
action-air pushing at you reaction- balloon going away from you
Click here for Example.

18. 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

19. 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

20. 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

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

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

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