A small rock with mass 0.18 kg is released from rest at point a, which is at the top edge of a large, hemispherical bowl with radius r = 0.50 m. assume that the size of the rock is small compared to r, so that the rock can be treated as a particle, and assume that the rock slides rather than rolls. the work done by friction on the rock when it moves from point a to point b at the bottom of the bowl has magnitude 0.22 j. between points a and b, how much work is done on the rock by the normal force?