1. MOTION & FORCE

2. Balanced and Unbalanced Forces
action exerted on a body in order to change body’s state of rest or motion.
has magnitude and direction.
NET FORCE
combination of all forces acting on an object.
BALANCED FORCES
Objects either do not move or move at constant velocity.
UNBALANCED FORCE
any change in an object’s state of motion or rest.

3. FRICTION
force that opposes motion between two surfaces that are in contact.
opposes applied force.

4. STATIC FRICTION
resists initiation of sliding motion between two surfaces that are in contact and at rest.
is greater than kinetic friction.
Object not moving

5. KINETIC FRICTION
opposes movement of two surfaces that are in contact and are sliding over each other.
Object is moving

6. TYPES OF KINETIC FRICTION

7. SLIDING FRICTION
When objects slide past each other

8. FLUID FRICTION
When an object moves through a fluid (air, water…) and surface of object

9. ROLLING FRICTION
When a round object rolls over a flat surface

10. FRICTION AND MOTION Friction can be helpful or harmful.
necessary to roll a vehicle or hold an object.
can also cause excessive heating or wear of moving parts.

11. HARMFUL FRICTION CAN BE REDUCED
Lubricants
Smooth surfaces
Replace with another type friction

12. HELPFUL FRICTION CAN BE INCREASED.
Make surfaces rougher
Increase forces pushing together