Please Take Out Your Homework

1. Please Take Out Your Homework

3. FRICTION 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? • http://www.youtube.com/watch?v=yTKwS-J7qVE • A little bit of friction? • http://digg.com/video/the-science-of-figure-skating • 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.

12. Does Size Matter? I’m talking about Mass or surface area folks!

13. Friction DOES depend upon: 1. surface area in contact2. mass/gravity (weight) of object3. 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