when a circular body rolls down an incline, the instantaneous axis of rotation is the point of contact of the body and incline. So, the component of weight along the incline does apply some torque. so the friction has to act downwards. but we take it to be up the incline. why?

Question

anonymous · Answer

friction always opposes motion...there is no motion in the vertical direction then how?
there is only motion down the slope

anonymous · Answer

friction opposes RELATIVE motion between 2 bodies