Question

How to approximate friction coefficients between different materials?

Answer 1

I want to add friction forces to my computer game. I know there are tables for friction, however I don't think that encoding big table of coefficients (of size n2n2) is a good idea.

I thought, that there may exist some characteristic λλ for each material, so that friction between materials aa and bb is approximated by μa,b=f(λa,λb)μa,b=f(λa,λb) for some function ff.

Do such characteristic and function ff exist? Note that I need this for computer game and I don't need big accuracy, only correct behavior.

Answer 2

The friction force is the force exerted by a surface when an object moves across it - or makes an effort to move across it.

The frictional force can be expressed as

Ff = μ N                     (1)

where

Ff = frictional force (N, lb)

μ = static (μs) or kinetic (μk) frictional coefficient

N = normal force between the surfaces (N, lb)

There are at least two types of friction forces

kinetic (sliding) friction force- when an object moves

static friction force - when an object makes an effort to move

For an object pulled or pushed horizontally the normal force - N - is simply the gravity force - or weight:

N = Fg

    = m ag                         (2)

where

Fg = gravity force - or weight (N, lb)

m = mass of object (kg, slugs)

ag = acceleration of gravity (9.81 m/s2, 32 ft/s2)

The friction force due to gravity (1) can with (2) be modified to

Ff = μ m ag                      (3)



Hope it's help you