13-67. A sled and rider, weighing 30 lb and 150 lb, respectively, travel down a smooth slope that has the shape shown. If the rider does not hold on to the

sides of the sled, determine the normal force which he exerts on the sled when the sled is (a) at point B, where it has a velocity of 15 ft/s, and (b) at some point C in mid air. Problem 13-67 y A 20 ft 20 ft -y = 20 cos -20 ft- cosx -20 ft- B X C