A 14.0 kg block is dragged over a rough, horizontal surface by a 87.0 N force acting at 20.0° above the horizontal. The block is displaced 6.50 m, and the coefficient of kinetic friction is 0.300. (b) Find the work done on the block by the normal force. J (c) Find the work done on the block by the gravitational force. J I thought normal force was mg which turned out wrong. For gravitational force, I tried force times delta r times cos theta, but that also turned out wrong as well.