1. PLEASE TAKE OUT YOUR HOMEWORK

3. Friction - a force that opposes motion, or “pushes back” when two surfaces are touching. It’s always around and it affects everything.

4. WITHOUT FRICTION…

5. FRICTION- WORKS AGAINST YOU …..BUT IT CAN BE HELPFUL! WHEN DO I WANT…  A lot of friction? A lot of friction?  http://www.youtube.com/watch?v=yTKwS-J7qVE http://www.youtube.com/watch?v=yTKwS-J7qVE  A little bit of friction? A little bit of friction?  http://digg.com/video/the-science-of-figure-skating http://digg.com/video/the-science-of-figure-skating  http://www.nbclearn.com/olympics http://www.nbclearn.com/olympics

6. FRICTION TYPES AND PARTS…  There are three Basic Types of Friction  Static  Kinetic  Fluid

7. TYPES OF FRICTION: 1) Static friction: Friction that resists the initiation (start) of sliding motion between two objects at rest. Keeps things stopped

8. TYPES OF FRICTION: 2) Kinetic friction: The force that opposes the movement of two surfaces that are in contact and moving over each other. To make something move, you just overcome static friction by pulling with a force larger than kinetic friction.

9. TWO TYPES OF KINETIC FRICTION: a) Sliding – the objects are sliding b) Rolling – the objects are rolling. Rolling is usually less than sliding.

10. TYPES OF FRICTION: 3) Fluid friction: The friction between layers of a fluid. 2 types- Liquid and Gas Liquid- water, oil etc. Gas - Air

11. TYPES OF FRICTION: Described by viscosity. Viscosity – the “thickness” of a fluid. Low viscosity = “thin;” High viscosity = “thick” or “viscous.” The less viscous a fluid is, the easier it moves.

13.  Friction DOES depend upon: 1. surface area in contact 2. mass/gravity (weight) of object 3. coefficient of friction – “mu”(the texture of the surface)

14. FRICTION IS CUMULATIVE  Small amounts of friction in a system add up to become a large amount of friction.

15. TEXTBOOK FRICTION…CHALLENGE