The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Raymond A. Serway, & Jerry S. Faughn. College Physics Sixth Edition. Pacific Grove: Thomson Learning Inc, 2003: 102.||
|Johnson, Clifford V. Friction. Microsoft Encarta Online Encyclopedia 2007.||
|Tadeusz, Burakowsk and Tadeusz, Wierzchon. Surface Engineering of Metals: Principles, Practices, Technologies. CRC Press, 1999: 143.||"The Coefficient of friction for snow or ice is only 0.03 because due to local very high pressure the temperature of water -ice phase transformation is lowered and a layer of water is created. At low temperatures (-40 C and lower) the layer of water is not formed and the coefficient of friction rises to a value normal for two sliding solid surfaces, i.e., 0.7 to 1.2".||0.03|
|Baker, J.S. Traffic Accident Investigation Manual. Evanston: Northwestern University, 1975: 210.||
|Gleason, J. Andrew. Preliminary results of snow surface friction coefficient measurements. International Snow Science Workshop. Penticton, BC, 2002.||"A coefficient of dry static friction was calculated for each snow type. Coefficients ranged from 0.53–1.76. Some of these coefficients were compared to shear strength numbers derived from shear frame measurements on the previous surface layer 24 hours after new snow fell on the surface."||0.53–1.76 (static)|
The coefficient of friction is a dimensionless quantity that quantifies the amount of friction between two surfaces. The symbol for coefficient of friction is μ (mu) and is defined as follows:
μ = ƒ /N
ƒ is the friction force and
N is the normal force between the two surfaces in contact.
Since the friction force is less than the normal force for most materials, is usually between 0 and 1.
There are two types of friction; static and kinetic. Static friction is the the force required to move an object from it's stationary state. Kinetic friction is the force required to keep the object in motion. Since it is harder to get an object in motion than it is to keep an object in motion, the coefficient of static friction is always greater than the coefficient of kinetic friction.
The coefficient of friction is the quotient obtained by dividing the value of the force necessary to move one body over another at a constant speed by the weight of the body. Coefficient of friction varies with temperature, pressure, and density. The condition that the material is in greatly affects it's coefficient of friction. For example the coefficient of kinetic friction for waxed wood on wet snow is 0.1 but for waxed wood on dry snow is 0.4.
Tabraiz Rasul -- 2007
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