In the human arm, the forearm and hand pivot about the elbow joint. consider a simplified model in which the biceps muscle is attached to the forearm 3.80 cm from the elbow joint. assume that the person's hand and forearm together weigh 15.0 n and that their center of gravity is 15.0 cm from the elbow (not quite halfway to the hand). the forearm is held horizontally at a right angle to the upper arm, with the biceps muscle exerting its force perpendicular to the forearm. a) the force exerted by the biceps when the hand is empty= 59.2 n b) when the person holds a 80.0-n weight in his hand, with the forearm still horizontal. the center of gravity of this weight is 33.0 cm from the elbow the force of the bicep= 754 n c) under the conditions of part b, find the magnitude of the force that the elbow joint exerts on the forearm. d)while holding the 80.0-n weight, the person raises his forearm until it is at an angle of 53.0 ? above the horizontal. if the biceps muscle continues to exert its force perpendicular to the forearm, what is this force when the forearm is in this