A garden sprinkler has four rotating arms, each of which consists of two horizontal straight sections of

Question:

A garden sprinkler has four rotating arms, each of which consists of two horizontal straight sections of pipe forming an angle of 120 ?. Each arm discharges water at a rate of 5gal/min with a velocity of 60 ft/s relative to the arm. Knowing that the friction between the moving and stationary parts of the sprinkler is equivalent to a couple of magnitude M = 0.275 lb ?? ft, determine the constant rate at which the sprinkler rotates (1 ft3 = 7.48 gal).