posted by Anonymous .
Starting from rest, a 5.0 kg block slides 2.5 m down a rough 30.0 degrees incline in 2.0s. Determine (a) the work done by the force of gravity. (b) the mechanical energy lost due to friction, and (c) the work done by the normal force between block and incline.
I know how to do a but I don't know how to do (b) or (c).