Undergrad Difference Between Resistance Force and Friction Coefficient?

[tymi9]

Hi
I have been wondering what is the difference between resistance force and friction coefficient. While doing research online I could not find a clear answer. Maybe someone here will now

 

[Dale]

Well, the units for one. The friction force has units of Newtons, and the friction. Coefficient is dimensionless.

 

[hutchphd]

I will assume that "resistance force" is another name for the more common "frictional force".
When two surfaces are ~smooth it is approximately true that the friction force is proportional to how strongly the surfaces are pushed together (this is the Normal force). And so we write that $$F_{friction}=\mu N$$

 

[Lnewqban]

Hi
I have been wondering what is the difference between resistance force and friction coefficient. While doing research online I could not find a clear answer. Maybe someone here will now

One is a force, the other is a ratio between two forces: normal and friction.

 

[tymi9]

Oh ok now I get it. thanks

However, is there a way to calculate the friction coefficient?

 

[hutchphd]

Not in a simple way. You should well know that it depends upon a lot of different things (like cleanliness of surfaces, moisture, temperature, etc). I think you can look up measured values for various combinations of surfaces. And the supposition that the ratio is constant is does not always hold. It is overemphasized in introductory physics because the problems are easy to formulate !

 

[Lnewqban]

Oh ok now I get it. thanks

However, is there a way to calculate the friction coefficient?

Please, see:
https://nfsi.org/wp-content/uploads/2013/10/Determining.pdf

 

[Dale]

Oh ok now I get it. thanks

However, is there a way to calculate the friction coefficient?

It is not simple to calculate, but it is rather straightforward to measure.

 

[Arjan82]

Let's just put here that resistance of an object can consist of multiple effects, friction is just one:
- Frictional resistance
- Form or pressure resistance (for not so aerodynamically shaped objects also called bluff body resistance)
- Wave resistance (only applicable to floating objects like ships)

So if you say what is the difference between a resistance force and frictional resistance force (I'm assuming both as a force now), then the resistance force usually contains frictional resistance but may contain other types of resistance as well, and is therefore always at least as big as the frictional resistance.