The figure (a) shows an outstretched arm with a mass of 4.0 {\rmkg}. The arm is 56 {\rm cm} long, and its center of gravity is 21{\rm cm} from the shoulder. The hand at the end of the arm holds a6.0-{\rm kg} mass. What is the torque about the shoulder due to the weights of the armand the 6.0-{\rm kg} mass? If the arm is held in equilibrium by the deltoid muscle, whoseforce on the arm acts 5.0 ^\circ below the horizontal at a point 18{\rm cm} from the shoulder joint (the figure (b)), what is theforce exerted by the muscle?
