Walker, Halliday & Resnick — Equilibrium and Elasticity: Problem 19

Figure 12-27 shows the anatomical structures in the lower leg and foot that are involved in standing on tiptoe on one foot, with the heel raised slightly off the floor so that the foot effectively contacts the floor only at point P. Assume distance a = 5.0 cm, distance b = 15 cm, and the person’s weight W = 1200 N. Of the forces acting on the foot, what are the (a) magnitude and (b) direction (up or down) of the force at point A from the calf muscle and the (c) magnitude and (d) direction (up or down) of the force at point B from the lower leg bones? (e) By how much is that force reduced if the person loses 22.0 kg of mass?