# What are factors that effect static friction?

marshall4
What are factors that effect static friction?

I know that mass has an effect and the surface area has no effect, but what are others that have an effect on static friction and that you would think have an effect even though they dont?

Homework Helper
FIrst let's separate the ideal world from the real world.

In an ideal world, fricitonal forces are due to 2 things, the coefficient of friction, "mu" and the normal force. FOr objects on flat surface, the normal force is equal in magnitude to the weight.
The "mu" depends on the materials of the two surfaces that are in contact.

With static friction, as opposed to kinetic friction, "mu" times normal force tells you the maximum possible force. Static friciton only shows up if some other force tries to push an object. IF nothing is pushing it, then no static friciton is necessary. Therefore static friciton is equal to the horizontal applied force on the object, up to that certain maximum limit.

It gets more complicated if forces are applied at angles, or if the object is on a slope.

Homework Helper
It is only independent of area if perfectly rigid bodies are assumed.

S = k log w
Originally posted by marshall4
What are factors that effect static friction?

I know that mass has an effect and the surface area has no effect, but what are others that have an effect on static friction and that
you would think have an effect even though they dont?

Static friction, also known as striction. See the physics of a dynamic brake.