A 4-lb moves in a straight line on horizontal plane whose coefficient of friction is 1/4. The air resistance amounts to v^2/16. The force acting upon the body is 4 lb, if v = 0 when s = 4 ft. Find v when s = 12 ft. Use g = 32 ft/<!--[if gte msEquation 12]>s2<![endif]--> s^2
