The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Sullivan, James F. Technical Physics.USA: Wiley, 1988: 204.||
|Encarta Encyclopedia 2004. Microsoft Corporation.||
|CRC Handbook of Physical Quantities. Boca Raton, FL: CRC Press, 1997: 145-156.||
|Weber, Robert L.; Manning, Kenneth V.; White, Marsh W. College Physics-4th Edition. USA: McGraw-Hill, 1965: 66||
|Determining the Coefficient of Friction - Succeed in Physical Science. School for Champions.||
Friction is a resistive force that prevents two objects from sliding freely agaisnt each other. The coefficient of friction (µ) is a number that is the ratio of the resistive force of friction (Ff) divided by the normal or perpendicular force (Fn) pushing the objects together. The formula is shown …
µ = Ff/Fn
The two main frictions used are static friction and kinetic friction. The coefficient of static friction for steel is around 0.6–0.15 and the coefficient of kinetic friction is around 0.09–0.6.
The making of steel involves many processes and stages. The basic raw materials are coal, iron ore, limestone and various chemicals. Coal is transformed into coke. The coke is combined with limestone and ore to the blast furnace where it is transformed into steel. The steel is made slabs which are then processed into the end product ordered by the customer. Turning coal into coke is necessary in making steel because coal does not burn hot enough to melt iron ore. Coal in its original state is mostly carbon, however there are impurities in coal such as tar, ammonia etc. These impurities keep coal from burning hot enough to reduce and melt iron ore, therefore they must be removed through the coking process. Oxygen is used to remove some of the carbon and small amounts of other metals are added to make the right kind of steel. The molten is then poured into ingots and left to cool. The steel is now ready to be processed into new products such as car bodies and steel cans.
Eunice Chen -- 2004
Friction is defined as the force opposing motion. One type of friction is static friction. The lower the static friction, the easier it is to make an object start moving. Friction is given with the equation
f = µN
where µ is the coefficient of friction and N is the normal force. Normal force is the force exerted on an object by the surface and it is perpendicular to the surface.
The procedure is as follows:
In order to find the component of the acceleration due to gravity parallel to the surface (a) you must first examine the graph of acceleration vs. time for each of the objects. Find the point where the graph stops a continual, gradual increase, and spikes. This is the parallel component of gravity. The acceleration is then used in the formula
sin-1 θ = (a/g)
where g is the acceleration due to gravity. This formula will give you the angle at which the static friction is overcome by the component of weight parallel to the surface. Next, you must calculate the coefficient of friction. At this angle, the parallel component of weight
W// = mg sin θ
equals the static friction
fstatic = µmg cos θ
Solve this for µ, and you find that
µ = tan θ
|Material||a (m/s2)||θ (°)||µstatic|
Michael Robbins, Daniel Saronson, Gafei Szeto, David Rozenberg -- 2005
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