engineering and 12th

1. Types of Friction

2. What is Friction?
 Friction is the resistance to the sliding,
rolling, or flowing motion of an object
due to its contact with another object.
 When a moving object comes in contact
with another object, friction is the
opposing force that slows or stops the
moving object.

3.  Without friction, an object would continue to move at
constant speed forever.
 The strength of the force of friction depends on the
type of surfaces and how hard the surfaces push
together.
 Rough surfaces produce greater friction than smooth
surfaces.

4.  Without friction you could not
 Write
 Drive a car
 Fly an airplane
 Why not?

5. Four Types of Friction
 Rolling Friction
 Static
 Sliding Friction
 Fluid Friction

6. What do all these things have in common?

7. Rolling Friction
 Rolling friction is friction
that occurs between surfaces
in motion in which one of
the surfaces is a wheel,
roller, or ball.
 Examples:
 Riding a bike – tires and ground
 Bowling – ball and lane

8. What do all these things have in common?

9. Static Friction
 Static friction is friction
that occurs when the
surfaces in contact are at
rest (not in motion).
 Examples:
 A book resting on a desk.
 A potted plant sitting on a
sidewalk.

10. What do all these objects have in common?

11. Sliding Friction
 Sliding friction is
friction that occurs
when solid surfaces
slide over one another.
 Examples:
 Writing – pencil point and
paper
 Combing your hair –
surface of comb and
strands of hair

12. What do all these things have in common?

13. Fluid Friction
 The force that tries to slow objects down when they
move through a liquid or a gas. It's also known as
"drag", or "air resistance".
 All gases and liquids are fluids.
 An airplane and a swimmer both experience fluid
friction.

14. Ways to Reduce Friction
 Smooth the surface
 Replace rolling with sliding
 Add oil or another type of lubricant

15. Friction Song
 What is friction?
 Friction Video

16. Gravity and Free Fall
 An object is in free fall when the only
force acting on the object is gravity.
 Free-falling objects do not encounter
air resistance.
 In free fall, the force of gravity is an
unbalanced force.

17. Calculating Free Fall
All objects in free fall accelerate at the same rate –
9.8 m/s² - regardless of their mass.
in one second = 9.8 m/s²
in two seconds = 19.6 m/s²
in three seconds = 29.4 m/s²
in four seconds = ________
The velocity continues to increase as the object
falls.

18. Gravity, Free Fall, and Projectile Motion
 An object that is thrown is called a projectile.
 If there is no air resistance, an object that is dropped
and an object that is thrown are both in free fall.
 Without the force of air resistance, both objects will
hit the ground at the same time.

19. Gravity and Air Resistance
 Most objects falling through air
experience a type of fluid friction called
air resistance.
 Air resistance is not the same for all
objects.
 The greater the surface area of the
object the greater the air resistance.
 However, since the elephant has more
mass, it has more downward force of
gravity and falls faster.

20. What type of friction?

21.  Static Friction

22. What type of friction?

23.  Rolling Friction

24. What type of friction?

25.  Fluid Friction

26. What type of friction?

27.  Static Friction

28. What type of friction?

29.  Sliding Friction

30. What type of friction?

31.  Fluid Friction