This document defines key terms and concepts related to friction such as static friction, kinetic friction, rolling friction, coefficient of friction, normal force, air resistance, and terminal velocity. It also asks guide questions about what friction is, the different types of friction and how they differ, how friction is described, what air resistance is, how terminal velocity is achieved, and how to increase or decrease friction.

2. Guide questions
 What is friction?
 What are the types of friction? How do
they differ from each other?
 How do we describe friction?

3. Guide questions
 What is air resistance?
 How does a body attain terminal
velocity?
 How do we increase/decrease friction?

4. Key terms
 Friction force (Ff) – a force that tends
to oppose motion
 Coefficient of friction (µ) – the ratio
of the friction force to the normal force

5. Key terms
 Static friction – the type of friction
that exists between the contact surfaces
of two bodies at rest
 Kinetic friction – the force that
opposes sliding motion

6. Key terms
 Rolling friction – the force that
opposes rolling motion
 Normal force (Fn) – the force pressing
two contact surfaces together

7. Key terms
 Air resistance – the friction between
air and a body moving through it
 Terminal velocity – the velocity
acquired by a freely falling body when
its weight equals the upward force
exerted by air

8. Cause

10. Types

11. Types

12. Types

13. Types

14. Properties

15. Properties

16. Properties

17. Properties

18. Properties

19. Properties

20. Air resistance

21. Terminal velocity

22. Terminal velocity

23. Advantages

24. Advantages

25. Advantages

26. Advantages

27. Disadvantages

28. Disadvantages

29. Disadvantages