Friction is the force created when two objects touch each other. It is created opposite the direction of movement or any force prompting movement. It is caused by the electromagnetic forces in charged particles on the surface of the objects.
Ff = Fn*µ
This means that the friction force is equal to the normal force(Fn) multiplied by the friction coefficient(µ). The normal force is how much force is exerted on one of the objects to resist some force pushing them together (normally the force pushing them together is gravity). The friction coefficient is a number specific to each material.
Even though we overcome friction force everyday, it can add up very quickly. Try weaving the pages of two phone books together. Pretend that you are shuffling a deck of cards, but with book pages instead. Now try to pull them apart. The friction between the pages makes it nearly impossible, if the pages are woven together correctly. Two perfectly weaved phonebooks could withstand thousands of Newtons of force.
1. Which type of friction applies to the phonebooks?
2. What factors influence the coefficient of friction?
3. Can you think of an example of how friction effects our daily lives?