This is not a specific problem. It pertains to all the problems I'm working on and only requires that I have one concept explained. If an object is being pulled up a plane by a force parallel to the plane, does the friction work against the parallel component of the gravity or the force pulling the object up? I have the parallel component of the gravity as weight_object * cos(angle), the pulling force in the exact opposite direction, and the friction as u * weight_object * cos(angle) The problem is I don't see which way to apply the friction. If the object was sliding down the plane, then friction would work against the gravity force. But shouldn't the friction also work against the act of pulling the object up the plane? I don't know if that means I ignore the friction, apply it in one direction only, or do something else to calculate the "net" friction force.