Assume the resistive force acting on a speed skater is proportional to the square of the skater's speed v and is given by f = 2kmv 2, where k is a constant and m is the skater's mass. The skater crosses the finish line of a straight-line race with speed vi and then slows down by coasting on his skates. Show that the skater's speed at any time t after crossing the finish line is v(t) = vi/(1 1 ktvi).