Doing some midterm review and I got stuck on this question. Starting from rest, a 5.0 kg block slides 2.1 m down a rough 30.0° incline. The coefficent of kinetic friction between the block and the incline is µk = 0.436. Determine the work done by the friction force between block and incline. My first thought was mgµk times distance, since work equals force times distance, but that didn't work. I'm not sure if the fact that friction is working against mg(sin theta) has anything to do with anything. If someone could point me in the right direction, I'd appreciate it.