# Physics

The Achilles tendon, which connects the calf muscles to the heel, is the thickest and strongest tendon in the body. In extreme activities, such as sprinting, it can be subjected to forces as high as 13.0 times a person's weight. According to one set of experiments, the average area of the Achilles tendon is 78.1 mm^2, its average length is 25.0 cm, and its average Young's modulus is 1474 MPa.

A)How much tensile stress is required to stretch this muscle by 5.00% of its length?
I first changed the units on the numbers:
78.1mm^2= .0781 m^2
25cm= .25m
1474MPa= 1.474*10^9 Pa
5% length= .0125 m

I tried using this equation:
F= YA/L *(delta)L

I got the answer 5755970, and they want the answer in Pa.

B)If we model the tendon as a spring, what is its force constant?

F=kx
Force from above part/.25m=k ??

C)If a 75.0 kg sprinter exerts a force of 13.0 times his weight on his Achilles tendon, by how much will it stretch?

1. 👍
2. 👎
3. 👁
1. You erred on changing square mm to square meters. There are 10^6 mmsquared in 1m^2, not 1000.

b) yes, force corrected.
c) if it is linear, then do the math F=kx

1. 👍
2. 👎
👤
bobpursley
2. I'm still getting A wrong....

F=(1.474*10^9)(7.81*10^-5)/(.25) *.0125

=5755.95 Pa

1. 👍
2. 👎
3. achilles

1. 👍
2. 👎
4. A) 7.7*10^7 Pa

1. 👍
2. 👎
5. k= A(Y)/L

MPa=Pa(1/1000)^2(mPa)

K=4.4*10^5

1. 👍
2. 👎

## Similar Questions

1. ### Phychology CHECK my answers

My answers have the star 1. The nervous system is the body’s ______________ network. (1 point) communication*** organization reactive production 2. The central nervous system (CNS) consists of the brain and the ___________. (1

2. ### chem

rank strongest acid to weakest acid? rank strongest acid to weakest acid H3CNH2 CH3C (triple bond) CH CH2=CHCH3 H20 CH4 i tried to rank them using the Pka values but I couldn't find the pKa value of the alkyne and I thought the

3. ### Chemistry

While you are doing heavy work, your heart pumps up to 25.0 L of blood per minute. Your muscles get about 80% by volume of your blood under these conditions. What volume of blood in quarts is pumped through your muscles in 107

4. ### Physics

A 13 cm long animal tendon was found to stretch 3.8 mm by a force of 13 N. The tendon was approximately round with an average diameter of 9.0 mm. Calculate the elastic modulus of this tendon.

1. ### College Physics

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. The Achilles tendon pulls straight upward on the heel bone of his foot. This tendon is 25 cm long

2. ### Biology -Nervous System

1. Explain why the knee-jerk and Achilles reflexes are important in walking.

3. ### Math

A calf is tied with a rope of length 6m at the corner of a square grassy lawn of side 20m. If the length of the rope is increased by 5.5m, find the increase in area of grassy lawn in whi the calf can graze.

4. ### science

is quadriceps muscles in the leg an example of a smooth muscle? Answer: No. smooth muscles control breathing, blood pressure, and line the inside of our organs.

1. ### Chemistry

Which of the following is the strongest acid? 1. HNO2 4. H2SO3 2. H2CO3 5. HFO 3. HC1O3 6. H2O I'm really stuck, I know none of these are a "strong acid." I think the strongest might be HClO3 because Cl has the highest oxidation

2. ### physics

As a woman walks, her entire weight is momentarily supported on the heel of one shoe. Calculate the pressure exerted on the floor by a high-heel shoe worn by a 50-kg woman if the heel has an area of 2.0cm^2. Express the pressure

3. ### Chemistry

Two lists of nucleophiles: H2O CH3CH2OH H3CO- CH3COO- OH- OH- H2N- CH3CH2O- H3COH (CH3)3CO- The first part is to give the strongest nucleophile in group 1. I picked H2N-because its the strongest base. Part two asks for the BEST

4. ### Science help ASAP

1. In which way does the circulatory system rely on the skeletal system? Glucose is secreted by compact bone as an energy source for blood. Spongy bone stores minerals needed by blood cells. Bones provide a source of oxygen to