Friction

1
Friction
2
Friction makes it possible

• To walk
• Use wheeled vehicles
• Sit
• Hold books

3
Which is not something fiction helps you do?
iRespond Question
F
Multiple Choice
A.) Float in outer space.
B.) Walk
C.) Sit in a seat.
D.) Hold things
E.)
4

• Friction is a force that occurs when 2 surfaces
  oppose each other.

5
Friction is a force
iRespond Question
F
Multiple Choice
A.) True
B.) False
C.)
D.)
E.)
6

• Rub your hands together to produce friction.

7
Types of friction

• Static
• Sliding
• Rolling
• Fluid

8
Which is not a kind of friction?
Which is not a type of friction?
iRespond Question
F
Multiple Choice
A.) Static
B.) Kinetic/Sliding
C.) Slippery
D.) Rolling
E.) Fluid
9
Static

• Friction that acts on something that is not
  moving
• Piano is held in place by static friction
• Static friction keeps you in your seat
• No heat or wear is generated

10
Sliding

• Force resulting when pushing or pulling an object
  over a surface.
• Moving daypushing a box across the floor
• Heat and wear can result

11
Rolling

• Contact is reduced because of rollers or wheels
  or ball bearings.
• Skate boards have ball bearings in the wheels.
• A cart has wheels.
• Less heat and wear will result.

12
Fluid friction

• Resistance from a liquid or air.
• Stirring a thick batter
• Walking through water
• Olympic bike riders

13
The wheels on a car are an example of what type
of friction?
iRespond Question
F
Multiple Choice
A.) Static
B.) Sliding
C.) Rolling
D.) Fluid
E.)
14
A box sitting on a slope is an example of which
type of friction?
iRespond Question
F
Multiple Choice
A.) Static
B.) Rolling
C.) Fluid
D.) Sliding
E.)
15
Air resistance is what kind of friction?
iRespond Question
F
Multiple Choice
A.) Static
B.) Sliding
C.) Rolling
D.) Fluid
E.)
16
Mu

• is the coefficient of friction.
• This depends on the two surfaces involved.

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Typical values of Mu

• Wood on wood .25-.5(no units)
• Glass on glass .9-1.0
• Steel on steel .6
• Steel on steel with oil .09
• Rubber on dry pavement 1.0
• Ski on snow .04
• Teflon on teflon .04

18
Which of the following is true about Mu?
iRespond Question
F
Multiple Choice
A.) It is always the same number
B.) It is the "Coefficient of friction"
C.) It doesn't depend on the surfaces involved
D.)
E.)
19
Assignment

• Name 2 sports where friction is helpful and
  needed. Explain
• Name 2 sports where friction is reduced for
  better performance. Explain

20
Reducing friction

• A smooth surface does demonstrate as much
  friction as a rough surface.
• A lubricant can be used to reduce friction.

21
You can get rid of friction by
iRespond Question
F
Multiple Choice
A.) making the surfaces rougher
B.) using lubrication
C.) there is nothing you can do to reduce friction
D.)
E.)
22
Which of the following are true about friction?
iRespond Question
F
Multiple Choice
A.) We couldn't live without it
B.) It depends on the two surfaces
C.) It can be a bad thing
D.) All of the above
E.) None of the above