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In [[solid mechanics]], the '''Young's modulus''' or '''modulus of elasticity''' (and also '''elastic modulus''') is a measure of the stiffness of a given material. It is defined as the limit for small strains of the rate of change of [[Stress_(physics)|stress]] with [[strain]].  This can be experimetally determined from the [[slope]] of a [[stress-strain curve]] created during [[tensile test]]s conducted on a sample of the material.

The Young's modulus allows [[engineer]]s and other scientists to calculate the behavior of a material under load.  For instance, it can be used to predict the amount a wire will extend under tension, or to predict the load at which a thin column will [[buckle]] under compression.  Some calculations also require the use of other material properties, such as the [[shear modulus]], [[density]] or [[Poisson's ratio]].

For many materials, Young's modulus is a constant over a range of strains. Such materials are called '''linear''', and are said to obey [[Hooke's law]].  Examples of linear materials include [[steel]], [[carbon fiber]] and [[glass]].  [[Rubber]] is a '''non-linear''' material.

<table border="1">
<caption>Approximate Young's Moduli of Various Solids</caption>
<tr> <td>Material</td> <td align="center">Young's modulus (E) in MPa</td> <td  align="center">Young's modulus (E) in psi</td> </tr>
<tr> <td>Soft [[cuticle]] of pregnant [[locust]]</td> <td align="center">0.21</td> <td  align="center">30</td> </tr>
<tr> <td>[[Rubber]] (small strain)</td> <td align="center">6.9</td> <td  align="center">1000</td> </tr>
<tr> <td>[[Shell]] membrane of [[egg]]</td>  <td align="center">7.58</td> <td  align="center">1100</td> </tr>
<tr> <td>Human [[cartilage]]</td> <td align="center">24.13</td> <td  align="center">3500</td> </tr>
<tr> <td>Human [[tendon]]</td> <td align="center">551.6</td> <td  align="center">80,000</td> </tr>
<tr> <td>[[Wallboard]]</td> <td align="center">1,379</td> <td  align="center">200,000</td> </tr>
<tr> <td>Unreinforced [[plastic]]s, [[polyethene]], [[nylon]]</td> <td align="center">1,379</td> <td  align="center">200,000</td> </tr>
<tr> <td>[[Plywood]]</td> <td align="center">6,895</td> <td  align="center">1,000,000</td> </tr>
<tr> <td>[[Wood]] (along grain)</td> <td align="center">6,895</td> <td  align="center">1,000,000</td> </tr>
<tr> <td>Fresh [[bone]]</td> <td align="center">20,685</td><td  align="center">3,000,000</td> </tr>
<tr> <td>[[Magnesium]] [[metal]]</td> <td align="center">41,370</td> <td  align="center">6,000,000</td> </tr>
<tr> <td>Ordinary [[glass]]es</td> <td align="center">68,950</td> <td  align="center">10,000,000</td> </tr>
<tr> <td>[[Aluminium]] [[alloy]]s</td> <td align="center">68,950</td> <td  align="center">10,000,000</td> </tr>
<tr> <td>[[Brass]]es and [[bronze]]s</td>  <td align="center">117,215</td> <td  align="center">17,000,000</td> </tr>
<tr> <td>[[Iron]] and [[steel]]</td> <td align="center">206,850</td> <td  align="center">30,000,000</td> </tr>
<tr> <td>[[Aluminium oxide]] ([[sapphire]])</td> <td align="center">413,700</td> <td  align="center">60,000,000</td> </tr>
<tr> <td>[[Diamond]]</td> </td> <td align="center">1,172,150</td> <td  align="center">170,000,000</td> </tr>
</table>

See also: [[Deformation]], [[Stress (physics)|Stress]], [[Strain]]

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====References====
* Adapted from the [[Wikipedia]] article, "Young's_modulus" [http://en.wikipedia.org/wiki/Young%27s_modulus http://en.wikipedia.org/wiki/Young%27s_modulus], used under the [[GNU Free Documentation License]]