If you are reading our site, you will remember us talking about Inertia. We said that the balls would keep rolling unless an outside force acts upon it and causes it to stop. It is obvious to us that in a game of pool the balls don't roll forever they always stop.  So what is acting on the balls causing then to stop rolling? The outside force in this case is called friction. Friction is a force that acts between two surfaces coming in contact. In pool the balls, and the felt top of the table are constantly in contact with each other, so there is always going to be friction in a game of pool. Friction is a drag force, therefore it will cause the pool ball to slow down, until it finally comes to a stop.

    There are two different kinds of friction:

There is a very simple formula related to friction, and because we are good guys we are going to share this formula with you. It is......

F = mN