Friction
Friction is another force that is all around us
Friction occurs whenever two objects are in contact with each other
Friction slows objects down as the two surfaces rub togather. So in which direction does friction act
The amount of friction depends on the roughness of the surfaces in contact.
There is more friction if the surfaces are rougher. There is less friction if the surfaces are smoother.
Reference
http://www.engineeringinteract.org/resources/parkworldplot/flash/concepts/friction.htm
