Click here to find out more about motion. Friction Friction is a force that interferes with the movement of one object rolling or sliding over another. It pushes in the direction opposite to which the object is moving. Friction has many causes. One important cause is the roughness of the rolling or sliding surface.
Rough surfaces have tiny projecting irregularities.
These interlock as one surface rolls or slides over another and resists motion. Smoothing the surfaces can reduce friction. Click here to find out more about friction. All rights reserved.