Hi PF, I have a question. Say a particle describes a circular motion over a table. We have that the modulus of the centripetal force must equal the one of the static friction force, right? And according to Newton's second law the frictional force must be parallel to the radius pointing at the particle, but in the opposite direction. However I thought that the frictional force always point in the opposite direction of motion. In the case of a circular motion the centripetal acceleration always point through the center of the path while the motion is circular. Hence my question is : in what direction does point the frictional force in the case of a circular motion? (My guess is that it points in the opposite direction of the center of the path, while my intuition would say it's tangent to the circular path). Thank you.