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static friction

Started by December 12, 2014 05:57 AM
2 comments, last by cadjunkie 10 years, 2 months ago

since i cant find any info about this:

will

something that has area of 1 m^2 and mass of 1000 kg

have the same friction as the same material on same surface but

2 m^2 and 500 kg mass

?

If you are using simple dry friction then no.

Fs = mu*Fn

Where Fs is the shear force (or frictional force), Fn is the normal force and mu is the friction coefficient between the two surfaces. Assuming the surface is flat then the normal force is,

Fn = m*g,

Where m is mass and g is gravitational acceleration. So for shape 1 the normal force is approx 981N, and shape 2 its 490.5N. Given the same friction coefficient for each object shape 2 will experience half the shear force as it applies half the normal force of shape 1.

http://en.wikipedia.org/wiki/Friction

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thanks i thought there was a corelation to the surface area

Just for clarification for others reading this, there is no correlation between surface area and friction. Amontons' Second Law states "the force of friction is independent of the apparent area of contact." The difference in friction forces in your example comes from the difference in mass, not the difference in surface area.

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