Basic Biomechanics 5th Edition by Susan Hall

Exercise 18

A 35 N hand and forearm are held at a 45° angle to the vertically oriented humerus. The CG of the forearm and hand is located at a distance of 15 cm from the joint center at the elbow, and the elbow fl exor muscles attach at an average distance of 3 cm from the joint center. (Assume that the muscles attach at an angle of 45° to the bones.)
a. How much force must be exerted by the forearm flexors to maintain this position?
b. How much force must the forearm flexors exert if a 50 N weight is held in the hand at a distance along the arm of 25 cm?