1. Aim: How do we explain Newton’s first law of motion?

2. What is a Force?
A force is a push or a pull. Side note: All behavior in the universe can be reduced to 4 forces. What are these forces?

3. Newton’s 1st Law of Motion
Newton’s 1st Law (Law of Inertia) states the following: An object at rest will remain at rest unless acted upon by an external force. An object in motion will continue to stay in motion at constant velocity unless acted upon by an external force. Inertia- the tendency of an object to maintain its state of rest or its uniform motion unless acted upon by a force. (Inertia is not a force.)

4. Explain how Newton’s 1st Law Applies

5. Galileo and Friction

6. Turn and Talk: Newton’s 1st Law of Motion Thought question
Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock will
gradually stop.
b. continue in motion in the same direction at constant speed.

7. Mass What is mass? Mass is a measure of the inertia of a body.
Mass is a resistance to acceleration.

8. Turn and Talk: Inertia Thought question
Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.
Tosh is right because inertia refers to mass which is a resistance to acceleration. The smaller the mass, the less the object is resistant to change.

9. Regents Checkpoint 1
Which object has the most inertia? a) Bowling Ball b) Tennis Ball c) Feather d) Hammer

10. Regents Checkpoint 2 Which object has the greatest inertia?
A 5 kg object moving at a speed of 5.0 m/s
A 10 kg object moving at a speed of 3.0 m/s
A 15 kg object moving at a speed of 1.0 m/s
A 20 kg object at rest

11. Newton’s Second Law of Motion
Fnet = ma The net force acting on an object is equal to its mass times its acceleration. Force is measured in units called newtons. What is one newton equal to?

12. Net Force
The net force is the vector sum of all the forces acting on an object. Example:
17 N
4 N
What is the net force acting on the box? 13 N to the right