1. The problem statement, all variables and given/known data This is a conceptual question. I always thought that friction goes in the direction opposite of the intended motion. But then today my teacher put a ball in his hand and moved it horizontally back and forth. The ball remained stationary. Then he said static friction is moving in the direction of the motion. Then when he was discussing centripetal acceleration, he said that in a situation where you were in a car making a turn, the static friction is the force keeping you going in a circle. So the static friction is in the direction of the acceleration. Since when did static friction act in the direction of motion? Is it when the object is moving? And does this only apply to static friction or kinetic as well. In which types of situations is it in the opposite direction. 2. Relevant equations F= mu Fn 3. The attempt at a solution I pretty much outlined my views in the statement of the question. Please help.