When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm is 1.50 kg. If the biceps is connected to the forearm a distance d_biceps = 3.50 cm from the elbow, how much force F_biceps must the biceps exert to hold a 650 g ball at the end of the forearm at distance d_ball = 37.0 cm from the elbow, with the forearm parallel to the floor? How much force F_elbow must the elbow exert?
What is the horizontal distance between the elbow and the point where the weight of the forearm acts?