1. Lesson 20 Friction and Gravity

2. Friction
The force that two surfaces exert on each other when they rub against each other.
Strength of friction
How hard the surfaces push together
Types of surfaces involved
What is an example of friction?

3. Static Friction Sliding Friction Rolling Friction Fluid Friction
Types of Friction
Static Friction
Sliding Friction
Rolling Friction
Fluid Friction

4. Static Friction Friction that acts on objects that are not moving
Ex. Heavy treasure chest on floor

5. Sliding Fraction Occurs when two solid surfaces slide over each other
Ex. Adding sand to an icy path to avoid slipping

6. Rolling Friction Occurs when objects roll across a surface
Easier to overcome than sliding friction
Ex. Anything that rolls over a surface

7. Fluid Friction
Solid Object moves through fluid
Ex. Surfboard on water

8. Read the article on friction
Classwork
Read the article on friction
Answer the questions at the bottom (full sentences)
Keep volume at a whisper