As part of an exercise program, a 75-kg person does toe raises in which he raises his entire body weight on the ball of one foot (Fig. P11.63). The Achilles tendon pulls straight upward on the heel bone of his foot. This tendon is 25 cm long and has a cross-sectional area of 78 mm²and a Young€™s modulus of 1470 MPa.

(a) Make a free-body diagram of the person€™s foot (everything below the ankle joint). You can neglect the weight of the foot.

(b) What force does the Achilles tendon exert on the heel during this exercise? Express your answer in newtons and in multiples of his weight.

(c) By how many millimeters does the exercise stretch his Achilles tendon?

Figure P11.63:

- Tibia Achilles tendon- Ankle joint K4.6*-12.5