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Wallpaper uploaded by Oto Lopes

Friction

https://www.wallpaperflare.com/man-in-black-shirt-pushing-tire-on-pavement-during-daytime-wallpaper-zzhze

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FRICTION

Between Solids

http://www.somers.k12.ct.us/~mporter/images/PolarBearIce.jpeg

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I can . . .

identify which variables affect�friction between two surfaces.
develop an equation that predicts the amount of friction between two surfaces.
differentiate between�static and kinetic friction
recognize the importance of accounting for friction in real life problems.

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Image by mollyroselee from Pixabay

https://www.pxfuel.com/en/free-photo-xsfwl

Ice

Wood

Concrete

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https://pixabay.com/vectors/box-crate-wooden-box-wooden-wood-4989961/

Static Friction

Kinetic Friction

Wood

Concrete

Wood

Concrete

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Static Friction�The force which must be overcome to initiate movement.

Kinetic Friction�The force which must be overcome to maintain movement.

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0

1

2

3

4

5

6

7

8

9

10

11

FRICTION

PULL

1 kg�(10 N)

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Static Friction

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Static Friction

Kinetic Friction

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Static Friction

Kinetic Friction

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Wood on Epoxy

Maximum Static Friction

Kinetic Friction

Static Friction

Kinetic Friction

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Wood on Epoxy

Glass on Epoxy

Static Friction

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Wood on Epoxy

Glass on Epoxy

Glass on Ice

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0

1

2

3

4

5

6

7

8

9

10

11

1 kg�(10 N)

Rubber on Granite

Wood on Epoxy

Glass on Epoxy

Glass on Ice

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Maximum Static Friction

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Force of Friction

Pull on String

Static Friction

Kinetic Friction

Break Free of Static Friction

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Aluminum	Aluminum	Clean and Dry	1.05 - 1.35	1.4
Aluminum	Aluminum	Lubricated and Greasy	0.3
Aluminum-bronze	Steel	Clean and Dry	0.45
Aluminum	Mild Steel	Clean and Dry	0.61	0.47
Aluminum	Snow	Wet 0oC	0.4
Aluminum	Snow	Dry 0oC	0.35
Brake material2)	Cast iron	Clean and Dry	0.4
Brake material2)	Cast iron (wet)	Clean and Dry	0.2
Brass	Steel	Clean and Dry	0.51	0.44
Brass	Steel	Lubricated and Greasy	0.19
Brass	Steel	Castor oil	0.11
Brass	Cast Iron	Clean and Dry		0.3
Brass	Ice	Clean 0oC		0.02
Brass	Ice	Clean -80oC		0.15
Brick	Wood	Clean and Dry	0.6
Bronze	Steel	Lubricated and Greasy	0.16
Bronze	Cast Iron	Clean and Dry		0.22
Bronze - sintered	Steel	Lubricated and Greasy	0.13
Cadmium	Cadmium	Clean and Dry	0.5
Cadmium	Cadmium	Lubricated and Greasy	0.05
Cadmium	Chromium	Clean and Dry	0.41
Cadmium	Chromium	Lubricated and Greasy	0.34
Cadmium	Mild Steel	Clean and Dry		0.46
Cast Iron	Cast Iron	Clean and Dry	1.1	0.15
Cast Iron	Cast Iron	Clean and Dry		0.15
Cast Iron	Cast Iron	Lubricated and Greasy		0.07
Cast Iron	Oak	Clean and Dry		0.49
Cast Iron	Oak	Lubricated and Greasy		0.075
Cast iron	Mild Steel	Clean and Dry	0.4
Cast iron	Mild Steel	Clean and Dry		0.23
Cast iron	Mild Steel	Lubricated and Greasy	0.21	0.133
Car tire	Asphalt	Clean and Dry	0.72
Car tire	Grass	Clean and Dry	0.35
Carbon (hard)	Carbon	Clean and Dry	0.16
Carbon (hard)	Carbon	Lubricated and Greasy	0.12 - 0.14
Carbon	Steel	Clean and Dry	0.14
Carbon	Steel	Lubricated and Greasy	0.11 - 0.14
Chromium	Chromium	Clean and Dry	0.41
Chromium	Chromium	Lubricated and Greasy	0.34
Copper-Lead alloy	Steel	Clean and Dry	0.22
Copper	Copper	Clean and Dry	1.6
Copper	Copper	Lubricated and Greasy	0.08
Copper	Cast Iron	Clean and Dry	1.05	0.29
Copper	Mild Steel	Clean and Dry	0.53	0.36
Copper	Mild Steel	Lubricated and Greasy		0.18
Copper	Mild Steel	Oleic acid		0.18
Copper	Glass	Clean and Dry	0.68	0.53
Cotton	Cotton	Threads	0.3
Diamond	Diamond	Clean and Dry	0.1
Diamond	Diamond	Lubricated and Greasy	0.05 - 0.1
Diamond	Metals	Clean and Dry	0.1 - 0.15
Diamond	Metal	Lubricated and Greasy	0.1
Garnet	Steel	Clean and Dry		0.39
Glass	Glass	Clean and Dry	0.9 - 1.0	0.4
Glass	Glass	Lubricated and Greasy	0.1 - 0.6	0.09 - 0.12
Glass	Metal	Clean and Dry	0.5 - 0.7
Glass	Metal	Lubricated and Greasy	0.2 - 0.3
Glass	Nickel	Clean and Dry	0.78
Glass	Nickel	Lubricated and Greasy	0.56
Graphite	Steel	Clean and Dry	0.1
Graphite	Steel	Lubricated and Greasy	0.1
Graphite	Graphite (in vacuum)	Clean and Dry	0.5 - 0.8
Graphite	Graphite	Clean and Dry	0.1
Graphite	Graphite	Lubricated and Greasy	0.1
Hemp rope	Timber	Clean and Dry	0.5
Horseshoe	Rubber	Clean and Dry	0.68
Horseshoe	Concrete	Clean and Dry	0.58
Ice	Ice	Clean 0oC	0.1	0.02
Ice	Ice	Clean -12oC	0.3	0.035
Ice	Ice	Clean -80oC	0.5	0.09
Ice	Wood	Clean and Dry	0.05
Ice	Steel	Clean and Dry	0.03
Iron	Iron	Clean and Dry	1
Iron	Iron	Lubricated and Greasy	0.15 - 0.20
Lead	Cast Iron	Clean and Dry		0.43
Leather	Oak	Parallel to grain	0.61	0.52
Leather	Metal	Clean and Dry	0.4
Leather	Metal	Lubricated and Greasy	0.2
Leather	Wood	Clean and Dry	0.3 - 0.4
Leather	Clean Metal	Clean and Dry	0.6
Leather	Cast Iron	Clean and Dry	0.6	0.56
Leather fiber	Cast iron	Clean and Dry	0.31
Leather fiber	Aluminum	Clean and Dry	0.3
Magnesium	Magnesium	Clean and Dry	0.6
Magnesium	Magnesium	Lubricated and Greasy	0.08
Magnesium	Steel	Clean and Dry		0.42
Magnesium	Cast Iron	Clean and Dry		0.25
Masonry	Brick	Clean and Dry	0.6 - 0.7
Mica	Mica	Freshly cleaved	1
Nickel	Nickel	Clean and Dry	0.7 - 1.1	0.53
Nickel	Nickel	Lubricated and Greasy	0.28	0.12
Nickel	Mild Steel	Clean and Dry		0.64
Nickel	Mild Steel	Lubricated and Greasy		0.178
Nylon	Nylon	Clean and Dry	0.15 - 0.25
Nylon	Steel	Clean and Dry	0.4
Nylon	Snow	Wet 0oC	0.4
Nylon	Snow	Dry -10oC	0.3
Oak	Oak (parallel grain)	Clean and Dry	0.62	0.48
Oak	Oak (cross grain)	Clean and Dry	0.54	0.32
Oak	Oak (cross grain)	Lubricated and Greasy		0.072
Paper	Cast Iron	Clean and Dry	0.2
Phosphor-bronze	Steel	Clean and Dry	0.35
Platinum	Platinum	Clean and Dry	1.2
Platinum	Platinum	Lubricated and Greasy	0.25
Plexiglas	Plexiglas	Clean and Dry	0.8
Plexiglas	Plexiglas	Lubricated and Greasy	0.8
Plexiglas	Steel	Clean and Dry	0.4 - 0.5
Plexiglas	Steel	Lubricated and Greasy	0.4 - 0.5
Polystyrene	Polystyrene	Clean and Dry	0.5
Polystyrene	Polystyrene	Lubricated and Greasy	0.5
Polystyrene	Steel	Clean and Dry	0.3 - 0.35
Polystyrene	Steel	Lubricated and Greasy	0.3 - 0.35
Polyethylene	Polytehylene	Clean and Dry	0.2
Polyethylene	Steel	Clean and Dry	0.2
Polyethylene	Steel	Lubricated and Greasy	0.2
Rubber	Rubber	Clean and Dry	1.16
Rubber	Cardboard	Clean and Dry	0.5 - 0.8
Rubber	Dry Asphalt	Clean and Dry	0.9	0.5 - 0.8
Rubber	Wet Asphalt	Clean and Dry		0.25 - 0.75
Rubber	Dry Concrete	Clean and Dry		0.6 - 0.85
Rubber	Wet Concrete	Clean and Dry		0.45 - 0.75
Silk	Silk	Clean	0.25
Silver	Silver	Clean and Dry	1.4
Silver	Silver	Lubricated and Greasy	0.55
Sapphire	Sapphire	Clean and Dry	0.2
Sapphire	Sapphire	Lubricated and Greasy	0.2
Silver	Silver	Clean and Dry	1.4
Silver	Silver	Lubricated and Greasy	0.55
Skin	Metals	Clean and Dry	0.8 - 1.0
Steel	Steel	Clean and Dry	0.5 - 0.8	0.42
Steel	Steel	Lubricated and Greasy	0.16
Steel	Steel	Castor oil	0.15	0.081
Steel	Steel	Stearic Acid		0.15
Steel	Steel	Light mineral oil	0.23
Steel	Steel	Lard	0.11	0.084
Steel	Steel	Graphite		0.058
Steel	Graphite	Clean and Dry	0.21
Straw Fiber	Cast Iron	Clean and Dry	0.26
Straw Fiber	Aluminum	Clean and Dry	0.27
Tarred fiber	Cast Iron	Clean and Dry	0.15
Tarred fiber	Aluminum	Clean and Dry	0.18
Polytetrafluoroethylene (PTFE) (Teflon)	Polytetrafluoroethylene (PTFE)	Clean and Dry	0.04	0.04
Polytetrafluoroethylene (PTFE)	Polytetrafluoroethylene (PTFE)	Lubricated and Greasy	0.04
Polytetrafluoroethylene (PTFE)	Steel	Clean and Dry	0.05 - 0.2
Polytetrafluoroethylene (PTFE)	Snow	Wet 0oC	0.05
Polytetrafluoroethylene (PTFE)	Snow	Dry 0oC	0.02
Tungsten Carbide	Steel	Clean and Dry	0.4 - 0.6
Tungsten Carbide	Steel	Lubricated and Greasy	0.1 - 0.2
Tungsten Carbide	Tungsten Carbide	Clean and Dry	0.2 - 0.25
Tungsten Carbide	Tungsten Carbide	Lubricated and Greasy	0.12
Tungsten Carbide	Copper	Clean and Dry	0.35
Tungsten Carbide	Iron	Clean and Dry	0.8
Tin	Cast Iron	Clean and Dry		0.32
Tire, dry	Road, dry	Clean and Dry	1
Tire, wet	Road, wet	Clean and Dry	0.2
Wax, ski	Snow	Wet 0oC	0.1
Wax, ski	Snow	Dry 0oC	0.04
Wax, ski	Snow	Dry -10oC	0.2
Wood	Clean Wood	Clean and Dry	0.25 - 0.5
Wood	Wet Wood	Clean and Dry	0.2
Wood	Clean Metal	Clean and Dry	0.2 - 0.6
Wood	Wet Metals	Clean and Dry	0.2
Wood	Stone	Clean and Dry	0.2 - 0.4
Wood	Concrete	Clean and Dry	0.62
Wood	Brick	Clean and Dry	0.6
Wood - waxed	Wet snow	Clean and Dry	0.14	0.1
Wood - waxed	Dry snow	Clean and Dry		0.04
Zinc	Cast Iron	Clean and Dry	0.85	0.21
Zinc	Zinc	Clean and Dry	0.6
Zinc	Zinc	Lubricated and Greasy	0.04

Material Combinations Surface Conditions Static Coefficient , μ_s Kinetic Coefficient , μ_k

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Waxed Skis	Snow	Dry	0.1	0.05

Material Combinations Surface Conditions Static Coefficient , μ_s Kinetic Coefficient , μ_k

https://www.defense.gov/observe/photo-gallery/igphoto/2001328177/

Alejandro Pena

350 lbs

How hard must they pull to�get the sled moving?

How hard must they pull to keep the sled moving?

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μ_static> μ_kinetic

The coefficient of static friction�is ALWAYS greater than�the coefficient of kinetic friction

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Static Friction or Kinetic Friction?

STATIC!

KINETIC!

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STATIC KINETIC

μ_static> μ_kinetic

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http://mirrorimageorigin.collegepublisher.com/media/paper299/stills/91lgzfkc.jpeg

The car in front of you suddenly slams on it’s brakes.�You need to stop quickly, so you yell the “f” word!

FRICTION!

Fyzx!

or a four letter “f” word!

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Force of Friction

Force on Break Pedal

Static Friction

Kinetic Friction

Break Free of Static Friction

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15 N

13 N

Calculate the coefficient of kinetic friction.

13 N

15 N

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Free Body Diagram

Weight

Pull

Normal Force

Friction

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6.17 N

15.0 N

(15.0 – 6.18) N

20.0 N

18.0°

20.0cos18.0°

20.0sin18.0°

6.18 N

19.0 N

8.82 N

μ_k= 0.700

(1.53 kg)

Calculate the Acceleration.

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Free Body Diagram

friction

Weight

Pull

Normal Force

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Wallpaper uploaded by Oto Lopes

https://www.wallpaperflare.com/man-in-black-shirt-pushing-tire-on-pavement-during-daytime-wallpaper-zzhze

Free Body Diagram

friction

Weight

Push

Normal�Force

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27^º

75 lbs

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27°

μ_s= 0.40

27 lbs

Will the box slide?

75 lbs

27°

67 lbs

34 lbs

67 lbs

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Friction

Weight

Normal Force

Free Body Diagram

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27°

μ_s= 0.57

Will the box slide?

(max)

75 lbs

27°

67 lbs

38 lbs

34 lbs

67 lbs

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Draw the Free Body Diagram.�Calculate the coefficient of friction if the box just begins to slide at 28°.

28°

The mass of the box is “m”.

The weight of the box is “m∙g”.

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28°

m·g

m·g·sin(28°)

m·g·cos(28°)

m·g·sin(28°)

The mass of the box is “m”.

The weight of the box is “m∙g”.

28°

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28°

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28°