1. Chapter 12 What You Will Learn Friction Magnitude (size)
Section 3 Friction: A Force That Opposes Motion
Chapter 12
What You Will Learn
Friction
Magnitude (size)
Kinetic friction
Static friction

2. Chapter 12 What You Will Learn
Section 3 Friction: A Force That Opposes Motion
Chapter 12
What You Will Learn
8.2.a Students know a force has both direction and magnitude.
8.2.c Students know when the forces on an object are balanced, the motion of the object does not change.
8.2.d Students know how to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction.
8.2.e  Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction).

3. Activity: Fingerprints
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Activity: Fingerprints

4. Chapter 12 The Source of Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
The Source of Friction
When the hills and valleys of one surface stick to the hills and valleys of another surface, friction is created.
Friction is a force that stops motion between two surfaces that are touching.

5. Chapter 12 The Source of Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
The Source of Friction
Friction is usually greater between materials that have rough surfaces than it is between materials that have smooth surfaces.

6. Activity: Friction Materials
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Activity: Friction Materials

7. Chapter 12
Matter in Motion

8. Chapter 12 The Source of Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
The Source of Friction
As the force pushing surfaces together increases, the friction between the surfaces increases.

9. Activity: Feeling Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Activity: Feeling Friction

10. Chapter 12 Types of Friction There are two types of friction:
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Types of Friction
There are two types of friction:
kinetic friction
2. static friction

11. Activity: Two Frictions
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Activity: Two Frictions

12. Chapter 12 Types of Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Types of Friction
1. Kinetic friction is friction between moving surfaces.
The force of sliding kinetic friction is greater than the force of rolling kinetic friction.

13. Activity: Rolling vs. Sliding
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Activity: Rolling vs. Sliding

14. Chapter 12 Types of Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Types of Friction
2. Static friction can balance an applied force and can prevent changes in motion.

15. Chapter 12
Matter in Motion

16. Friction: Harmful and Helpful
Section 3 Friction: A Force That Opposes Motion
Chapter 12
Friction: Harmful and Helpful
Harmful Friction
(too little / too much)
Helpful Friction
(right amount)

17. DECREASE Harmful Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
DECREASE Harmful Friction
Lubricants
ex: motor oil, wax, and grease
decrease friction between the surfaces
can decrease harmful friction
Smooth the surfaces that rub against each other.

18. INCREASE Helpful Friction
Section 3 Friction: A Force That Opposes Motion
Chapter 12
INCREASE Helpful Friction
Make the surfaces that rub against each other rougher.
Increase the force pushing surfaces together.

19. Section 3 Friction: A Force That Opposes Motion
Chapter 12
The End