1. Motion and Forces
Section 2-3

2. What is a force? Push or pull one body exerts on another Push a door
Stretch a rubber band
Shove a book across the table
Some are obvious (car hits tree), others are not (floor pushing on feet).

3. Effects of Forces on Objects
Does the object move when a force is exerted on it?
Balanced forces: equal in size but opposite in direction (tug of war)
Unbalanced Forces: (Net forces) change the velocity (speed or direction) of the object

4. Inertia and Mass
Inertia: A moving object keeps moving and a stationary object remains stationary until a force acts on it.
Compare the inertia of bowling ball with tennis ball
More mass = more inertia

5. Newton’s first law
An object in motion remains in motion unless a net force acts on it. An object at rest remains at rest unless a net force acts on it. (INERTIA)
Wheelbarrow with rake on top strikes a rock. What happens?
Why do cars have seatbelts?

6. Friction
Force that opposes motion between two surfaces that are touching.
Amount of friction depends on: The kinds of surfaces, and the force pressing the surfaces together.