1. FRICTION

2. Any force that resists motion
It involves objects that are in contact with each other.
This is the force that keeps an object from sliding down and incline plane.

3. Friction
Friction is a force that resists the motion of two surfaces that are touching.
When a moving object comes in contact with another object, friction is the opposing force that slows or stops the moving object.

4. Some scientists believe that friction is caused by uneven surfaces of the touching objects – when rubbed together resistance is offered.
Experiments have shown that tiny particles are actually torn from one surface and imbedded in the other.
If two surfaces were carefully polished, there is a limit to the amount by which friction may be reduced. If made too smooth, the friction between them actually increases.

5. Types of Friction Static..prevents objects sliding
*Sliding...resists objects while they are moving
*Fluid…air or water

6. Examples of Friction Tires on the road Walking/Running Nails into wood
Sled on hill

7. Without friction, an object would continue to move at constant speed forever.
The strength of the force of friction depends on the type of surfaces and how hard the surfaces push together.
Rough surfaces produce greater friction than smooth surfaces.

8. Principles of Friction
Friction acts parallel to the surface that are in contact.
The direction that friction acts is OPPOSITE the direction of the motion (or intended motion).
Fnormal
Ffriction(k)
Fapplied
Fweight

9. Sliding Friction
A resistance to movement that is created when two things rub together.

10. Fluid Friction
The force that tries to slow objects down when they move through a liquid or a gas. It's also known as "drag", or "air resistance".
All gases and liquids are fluids.
An airplane and a swimmer both experience fluid friction.

11. Static Friction – the frictional force present just before motion begins. Starting Friction is when Static Friction is at is maximum.
Kinetic Friction – the frictional force present with motion
Note: Static Friction is usually higher than Kinetic Friction