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So in order to find stress i would Divided Force (Newtons ) by Area ( 0.0000000000785 m) will give me stress in pascals.. If 1 Pascal = 1 Pa = 1 N/m2 is the area 0.0000000000785 m or m2?

- alondra011
**Posts:**10**Joined:**Wed Oct 24, 2012 2:37 pm**Occupation:**Student**Project Question:**How does chemical lighting hair treatments affect the elasticity of hair?**Project Due Date:**11/20/12**Project Status:**I am just starting

I lost you at "I need to find area in meters" since area would be meter^2, not meters. A bundle of 100 hairs will have 100 times the area of one hair, and since area goes as diameter squared, the bundle of 100 will have 10 times the diameter of one hair. Thus diameter of one hair = (1/10) diameter of bundle of 100 = (1/10) * 1 mm = 0.1 mm = 1E-4 m = 100 micrometers.

- John Dreher
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**Posts:**294**Joined:**Sun Dec 25, 2011 8:33 am**Occupation:**Astronomer, Professor of Physics, SETI Researcher (retired)**Project Question:**n/a**Project Due Date:**n/a**Project Status:**Not applicable

alondra011 wrote:So in order to find stress i would Divided Force (Newtons ) by Area ( 0.0000000000785 m) will give me stress in pascals.. If 1 Pascal = 1 Pa = 1 N/m2 is the area 0.0000000000785 m or m2?

If you compute using scientific notation you are less likely to make arithmetical errors. Myself, I cannot decipher expressions like "0.0000000000785".

- John Dreher
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**Posts:**294**Joined:**Sun Dec 25, 2011 8:33 am**Occupation:**Astronomer, Professor of Physics, SETI Researcher (retired)**Project Question:**n/a**Project Due Date:**n/a**Project Status:**Not applicable

Thank you so much for everybody's help and support. My science fair came out super great I'm just waiting for y results . Thank you so much

- alondra011
**Posts:**10**Joined:**Wed Oct 24, 2012 2:37 pm**Occupation:**Student**Project Question:**How does chemical lighting hair treatments affect the elasticity of hair?**Project Due Date:**11/20/12**Project Status:**I am just starting

alondra011 wrote:So what I did was that I made a Bundle of 100 hairs and measure it. It was 1mm so I divided 1/100 = 0.01 . I need to find area in meters so I converted 0.01mm to a meter which equals to 0.00001m since we divided 0.01/1000.

0.00001m is the diameter but we need to find the radius to calculate area so it will equal to 0.000005m.

Am I correcT?

What justification do you have for dividing by 100 this early in the calculations?

If the diameter of a bundle of 100 hairs is 1mm, the radius of the bundle is 0.5 mm (radius = 1/2 the diameter), and the area of the bundle is 2*pi*(0.5*0.5) = aproximately 1.57 sq mm.

Now you get to divide this area by 100 hairs to get the cross section area of the average hair in the bundle = 0.0157 sq mm which is 0.0000000157 sq m (1.57 x 10**-8 m).

This cross sectional area in sq m is what you need in the formula.

-Craig

- Craig_Bridge
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