1. Friction

2. Friction: a force that opposes motion between two surfaces that are in contact.
Friction can cause a moving object to slow down and eventually stop.

3. When a force is applied to an object but does not cause the object to move.
Static means “not moving”
Contrasting examples…walking on asphalt and walking on ice
Static Friction

4. Kinetic Friction The friction between 2 moving surfaces
There are 2 main types:
Sliding friction
Rolling friction
Kinetic Friction

5. Sliding Friction (kinetic friction)
Force of sliding friction is usually greater than the force of rolling friction.
Example…ever tried to slide really large and heavy objects?
Sliding Friction (kinetic friction)

6. Rolling (Kinetic Friction)
The force of rolling friction is smaller than sliding friction.
If you put that large heavy object on wheels it be much easier to move!
Rolling (Kinetic Friction)

7. This includes air resistance as well as resistance in a liquid
Example…sky diving and swimming in a pool
Fluid Friction

8. Brakes in cars work by pressing pads together within the car’s wheel assembly. This resistance to the motion off the car results from which of the types of friction?
Sliding friction
Friction Review

9. The force of friction between a rock and the ground just before the rock starts to slide down a mountain slide.
Static friction, sliding friction, rolling friction or air resistance

10. The force of friction between a bike tire and the road as a cyclist skids to a stop
Static friction, sliding friction, rolling friction or air resistance

11. The force of friction that slows down a skier if she doesn’t wax the bottom of her skis.
Static friction, sliding friction, rolling friction or air resistance

12. The type of friction that you would want to increase if you were trying to walk across a large sheet of slick ice.
Static friction, sliding friction, rolling friction or air resistance

13. Put the different types of friction in order of strongest force to weakest force.
Static friction is strongest, followed by sliding friction, and then rolling friction, which is weakest.
Friction Review

14. The type of friction that athletes often try to reduce by wearing tight fitting outfits during races.
Static friction, sliding friction, rolling friction or air resistance

15. What is the force of friction between a rock and the ground just before the rock starts to slide down a mountain slide?
What is the force of friction between a bike tire and the road as a cyclist skids to a stop?
What is the force of friction that slows down a skier if she doesn’t wax the bottom of her skies?

16. What is the type of friction that you would want to increase if you were trying to walk across a large sheet of slick ice?
What is the type of friction that athletes often try to reduce by wearing tight fitting outfits during races?