1. Complex machines & FRICTION!!

2. Complex Machines
COMPLEX MACHINE: is a machine that consists of MORE than ONE simple machine.
Give me examples!!
Wine opener
Wheel barrow
Car

3. Friction
Friction: a force that OPPOSES motion between TWO surfaces that are in CONTACT.
THREE factors that affect the force of friction are the types of SURFACES involved and how hard the surfaces are PUSHED together. Also, the amount of SURFACE AREA!!
Friction acts in a direction OPPOSITE to the direction of the object’s motion. Without friction a moving object will not stop until it hits another object.
Give me some examples +/-
NOT IN NOTES
PUT IN NOTES

5. ADD IN NOTES:
Friction happens because NO surface is perfectly smooth!!

6. Friction produces HEAT energy!!
Add in notes:
Friction produces HEAT energy!!
As you rub two surfaces together those surface molecules start to move faster producing more heat energy.
Heat from friction can be useful.

7. Generally smooth surfaces produce LESS friction than rough surfaces.
Smooth vs. rough
Generally smooth surfaces produce LESS friction than rough surfaces.
Example: pushing a shopping cart across the Costco cement floors vs. pushing the cart across the parking lot outside of Costco.

8. Heavier vs. lighter
Friction INCREASES when surfaces push HARDER against each other.
Heavier objects push harder DOWNWARD onto the surface producing greater friction than something lighter.
EXAMPLE: RUBBING HANDS TOGETHER

9. Kinetic vs. static
Kinetic Friction is friction that is involved with MOVING objects
Static Friction is friction that is involved with STATIONARY (non-moving) objects.
Write this in notebook!!!

10. 4 types of friction: SLIDING (kinetic) ROLLING (kinetic)
FLUID (kinetic)
STATIC (static)
S(U)RFS

11. Occurs when two solid surfaces SLIDE over each other.
SLIDING FRICTION
Occurs when two solid surfaces SLIDE over each other.
Ex: a penguin sliding down a mtn he wouldn’t stop until he hit an iceberg.

12. Rolling friction
When an object ROLLS across a surface, rolling friction occurs.
Rolling friction is much EASIER to overcome than sliding friction for similar materials.
Ex: a bike

13. FLUID FRICTION
Fluids, such as WATER and AIR, are materials that flow easily.
Fluid friction occurs when a SOLID object moves through a FLUID. Fluid friction is EASIER to overcome than sliding friction.
Ex: Sliding on a dry slippin’ slide.

14. Static friction
Static friction acts between objects that are NOT MOVING. The force that’s keeping you from moving is static friction.
Ex: pushing a couch
If you don’t push hard enough the couch wont move. Whats keeping it there? Static bitches
Once counch moves what friction is it

15. Examples:
The force of friction between a bike tire and the road as a cyclist skids to a stop.
The force of friction that slows down a skier if she doesn’t wax the bottom of her skies.
The force of friction between a rock and the ground just before the rock starts to slide down a mountain.
The force of friction that a sky diver experiences.
The force of friction while driving a car.
The force of friction a fish experiences.
The force of friction that occurs while walking.

16. Strongest to weakest???