So, torque is given by I (moment of inertia) x angular acceleration. Let's say that the wheel is a hollow cylinder so the M.O.I is mr^2, I think. If a torque, T is applied to the wheel and there is a frictional force acting on the wheel, calculate the angular acceleration. Well, T - r(F) = I x a (r being the radius of the wheel). My question is, why does the frictional force cause a moment that opposes the motion of the wheel? I would've thought it was the other way around. If the frictional force is acting backwards then wouldn't it's moment with the centre of the wheel cause it to rotate in a clockwise direction? Is the frictional force actually acting backwards or do I have this mixed up? Apologies for not sticking to the headings but they don't show up when posting from a phone.