Young Modulus

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The Young Modulus

Stress and strain can be combined to give a property of a material. This property of the material is called the Young modulus and it is the same for any sample of the material; it does not depend on the size or shape of the sample.

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Young modulus

  • Young modulus gets it name from the scientist Thomas Young.
  • It is defined as the ratio of stress to strain.
  • The Young modulus can be written as:
    • Young modulus =stressstrain = \frac{stress}{strain}
    • E=σϵE = \frac{\sigma}{\epsilon}
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Stiffness of a material

  • The Young modulus represents the stiffness of a material.
  • Stiff materials have a small strain for large stresses.
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Gradient and Young modulus

  • The gradient of the linear section of a stress-strain graph is the Young modulus.

Determining the Young Modulus

The Young modulus can be determined simply. The simple method involves stretching a long thin wire and recording the stress and strain.

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  • Set up your equipment as shown.
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  • Determine the cross-sectional area of the wire by assuming a circular cross section.
    • A micrometer screw gauge would be the best piece of equipment to use here.
  • Determine the un-stretched length of the wire.
  • Add masses and record the extension of the wire. You can work out the applied force from the masses added.
  • For each set of masses added, you can obtain pairs of stress-strain values.
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  • The gradient of the linear section of a stress-strain graph is the Young modulus.

Jump to other topics

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4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

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8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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