How friction depends on surface area...


by s0ft
Tags: depends, friction, surface
s0ft
s0ft is offline
#1
Dec23-12, 11:01 PM
P: 77
I'd read that friction is independent of the surface area of the bodies in contact. But somewhere in the internet I found that this explanation was just a good approximation and that friction actually depends on area. Can anyone explain a bit more on this?
Phys.Org News Partner Physics news on Phys.org
Physicists consider implications of recent revelations about the universe's first light
Vacuum ultraviolet lamp of the future created in Japan
Grasp of SQUIDs dynamics facilitates eavesdropping
Woopydalan
Woopydalan is offline
#2
Dec24-12, 12:51 AM
P: 746
Just look at the equations for the force of friction..nowhere is the surface area of the object included
s0ft
s0ft is offline
#3
Dec24-12, 06:10 AM
P: 77
You can look @ http://zebu.uoregon.edu/1999/ph161/friction.html
and there you will find written friction is nearly or mostly independent of surface area. That must mean there is something more to it than just normal force and a constant.

AlephZero
AlephZero is online now
#4
Dec24-12, 09:06 AM
Engineering
Sci Advisor
HW Helper
Thanks
P: 6,383

How friction depends on surface area...


Quote Quote by s0ft View Post
That must mean there is something more to it than just normal force and a constant.
There is a lot more to friction than what you learn in a first course in mechanics. The Coulomb model of friction (the static and dynamic coefficients of friction are constants and independent of the normal force, surface area, etc) is a simple model of friction that works pretty well for "rigid" objects with "hard" surfaces moving fairly slowly, in orher words the situation you have in lab experiments. It is also simple enough to use in hand calculations.

Some students seem to get the wrong idea that Coulomb's "law" of friction is the same sort of law as Newton's "law" of gravity or the ideal gas "laws". It isn't.

More complicated models of friction include the flexibility of the objects that are in contact, and possibly the atomic structure of the materials as well, but the only practical way to use those models is in a computer simulation, not setting up and solving problems by hand.
s0ft
s0ft is offline
#5
Dec24-12, 09:42 PM
P: 77
Just asking, would it be possible to derive the simple : friction = μN expression from Coulomb's law for electric charges?


Register to reply

Related Discussions
Friction and Surface Area Introductory Physics Homework 1
Surface Area and Friction Introductory Physics Homework 7
Friction depends upon area or not? Classical Physics 4
Friction, heat, time & surface area Classical Physics 5
----friction Is Independant Of Surface Area------ Classical Physics 5