The bones of the forearm (radius and ulna) are hinged to the humerus and the elbow (see the figure below). The biceps muscle connects to the bones of the forearm about 2 cm beyond the elbow. Assume the forearm (measured from the elbow to the position where the person is holding the object in her hand) is of uniform density with a mass of 2 kg and a length of 40 cm.
When the humerus and the biceps muscle are nearly vertical and the forearm is horizontal, if a person wishes to hold an object of mass M = 1 kg and have her forearm remains motionless, what force must be exerted by her biceps muscle? To simplify this problem, assume the humerus bone and the biceps muscle are parallel to each other and that in the situation described in the problem they are perpendicular to the forearm.
