1. The Force
and Related Concepts

2. Force Can you define it? Definition:
The cause of acceleration, or the change in an object’s velocity
(or the push or pull on an object)
How can velocity change?
Many forces can act on an object at once.
The combination of all these forces is called…
Net Force

3. Balanced and Unbalanced
Balanced Forces
All forces on the object combine for a net force of zero
Balanced forces do not change the object’s motion
The object can be moving, but there is no change
Unbalanced Forces
Forces acting on the object combine to produce a nonzero net force
All the forces combine to act like a single force on the object
Motion is affected by an unbalanced force

4. Friction What is friction? Definition:
A force between two objects that are in contact that opposes the motion of either object
Friction happens as long as there is…
contact

5. Friction Frictional force varies with surface Air Resistance Examples
A form of friction between a moving object and air molecules
Depends on the size and shape of the object

6. Gravity What is gravity? Definition: Gravity does not require contact
The force of attraction between two particles
Gravity does not require contact
Affected by mass and distance
Not a one-way street