1. Chapter 13 Section 3 Newton’s Laws of Motion
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2. Chapter 13 Section 3 Part 1 Newton’s First Law of Motion
An object at rest remains at rest and an object in motion remains in motion unless acted on by an unbalanced force.

3. Objects at Rest
Objects will not start moving until a push or a pull is exerted on them.

4. Objects in Motion
An object moving at a certain velocity will continue to move forever at the same speed and in the same direction unless something stops it.
So, why do we wear seatbelts in cars?

5. Friction and Newton’s First Law
Friction is often the unbalanced force that causes objects to come to a stop.

6. Inertia a baseball than a piano.
Inertia is the tendency of all objects to resist any change in motion.
Mass is a measure of inertia.
Larger mass = more inertia
Example: It’s easier to push
a baseball than a piano.

7. When you stand while riding a bus, why do you tend to fall backward when the bus starts moving? Explain using Newton’s 1st Law and inertia.
Newton’s 1st Law - Both you and the bus were at rest. The bus started moving but no unbalanced force acted on your body so your body stayed at rest.
Inertia - You have inertia, and that makes you difficult to move, so when the bus started to move, you didn’t move with it.