A limit to friction?

[Visionary]

Two surfaces are placed. Surface block with the surface of the ground.

The Coefficient of Friction (COF) is 0.1 between them. Friction is because of force acting downwards.

The force is = x. By increase "x" to 100 times, will friction increase? I assume yes, but isn't there a limit?

Edited September 3, 2013 by Visionary

[J.C.MacSwell]

Two surfaces are placed. Surface block with the surface of the ground.

The Coefficient of Friction (COF) is 0.1 between them. Friction is because of force acting downwards.

The force is = x. By increase "x" to 100 times, will friction increase? I assume yes, but isn't there a limit?

It is also of course related to the forces acting parallel to that, resisting the motion. I believe the coefficient is fairly stable within the yield points of the surfaces for most materials. Beyond that, with the materials stressed beyond their elastic and ultimate limits, things would change considerably with a number of factors coming into play.

[Visionary]

Ah, I remember in my Physics class that the COF stays constant no matter what, wasn't sure till now.

Indeed, if the force of x increases the physical properties of that object could get damaged.

[J.C.MacSwell]

Ah, I remember in my Physics class that the COF stays constant no matter what, wasn't sure till now.

Indeed, if the force of x increases the physical properties of that object could get damaged.

I think "no matter what" may be a somewhat overstatement based on the simplest model, but it is usually fairly accurate in that range.

 

Keep in mind that static friction is usually greater than that once the motion has started.

 

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

[Visionary]

I agree.

Friction = COF x Normal Force

 

I assumed, by increasing N friction would not increase.

But indeed it will, but maybe the limit is when the object breaks.

[imatfaal]

I agree.

Friction = COF x Normal Force

 

I assumed, by increasing N friction would not increase.

But indeed it will, but maybe the limit is when the object breaks.

 

Remember that from a mechanics course and theoretical view that it is maximum friction which equals coefficient of static friction times the normal - the frictional force before movement will equal and oppose exactly any motive force upto the limit of mu_s * N. kinetic friction is not a equal and opposing force with a maximum in the same way

[Visionary]

It's amazing to find some coating materials can have COF of static & Kinetic be equal.

Like Teflon, if it's placed on two surfaces COF of S&K = 0.04

Edited September 3, 2013 by Visionary