Question

As a swimmer pulls his arm through the water, various muscles exert forces on the upper arm. The figure below shows a force F exerted on the humerus (upper arm bone) by the pectoral muscle. The muscle is connected to the bone d = 7.00 cm from the center point O of the shoulder joint. Find the magnitude of F, if this force's torque on the arm provides half of the total torque balancing the torque produced by the water pushing against the hand. (Let Fhand = 107 and D = 30.5 cm. )