The achilles tendon connects the muscles in your calf to the back of your foot. when you are sprinting, your achilles ten-don alternately stretches, as you bring your weight down onto your forward foot, and contracts to push you off the ground. a 70 kg runner has an achilles tendon that is 15 cm long with a typical 1.1 * 10-4 m2 area. a. by how much will the runner’s achilles tendon stretch if the maximum force on it is 8.0 times his weight, a typical value while running? b. what fraction of the tendon’s length does this correspond to?

A) We know that the gravitational Weight of a Body is given by,

The expression of young's modulus is given by,

Replacing the value of the force in the equation of young's modulis we have,

Re-arrange the equation for the rate of l, we have,

Our values here are giving by,

Replacing in the previous equation we have that,

We note that Achilles tendon stretch around 5mm

B) The strain is given by the equation,

The fraction of the tendon's lenght is the ratio of the change in lenght to the streched lenght, that is

The fraction of the tendon's lenght is 0.0333