A 4.0-kg block is lowered down a 37° incline a distance of 5.0 m from point A to point B. A horizontal force (F = 10 N) is applied to the block between A and B as shown in the figure. The kinetic energy of the block at A is 10 J and at B it is 20 J. How much work is done on the block by the force of friction between A and B?
(I can't find a picture of this, but the block is being lowered down an incline going right, and the horizontal force is directly left, parallel to the ground)
Ek = 0.5mv^2
Ep = mgh
(delta)E = Ef - Ei
The Attempt at a Solution
After some research, the answer is supposed to be -68 J
However, I'm stuck as to how I have to approach this problem. My initial idea was to determine the potential and kinetic energies of both A and B, and somehow use basic math and plug n' chug to get my answer. Is this the right approach?