Achilles -Tibia tendon- Ankle joint 不4.6 12.5 cm cm

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.). The Achilles
tendon pulls straight upward on
the heel bone of his foot. This tendon
is 25 cm long and has a crosssectional
area of 78 mm2 and a
Young’s modulus of 1470 MPa.
(a) Draw a free-body diagram of
the person’s foot (everything below
the ankle joint). Ignore 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?