The Achilles tendon connects the muscles in your calf to the back of your foot. When you are sprinting, your Achilles tendon 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 1.1×10−4m2 area.
A. By how much will the runner's Achilles tendon stretch if theforce on it is 8.0 times his weight?
B. What fraction of the tendon's length does this correspond?

Explanation:

Given:

Mass, M = 70 kg

Area, A = 1.1 × 10^-4 m^2

Achilles tendon length, l = 15 cm

= 0.15 m

Young modulus for tendon, E = 0.15 × 10^10 N/m^2

Young modulus, E = tensile stress/tensile strain

But,

Stress = force/area

Strain = extension/length

A.

Force = 8 × N

N = m × g

= 70 × 9.8 × 8

= 5488 N

Extension = (force × length)/(area × yound modulus)

= (5488 × 0.15)/(1.1 × 10^-4 × 0.15 × 10^10)

= 4.989 mm

= 0.005 m

B.

Fraction of length, x = extension/original length

= 0.005/0.15

= 0.033

= 3.3 %

the force represented by vector a is normal force. if the hockey puck is moving to the right, when it is hit with a significant force by the hockey stick the puck will move off in a different direction. correct on edge.