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Difference Between Young's Modulus & Second Moment of Area

  1. Nov 2, 2018 #1
    Hi all

    I was hoping someone could help explain the difference between Young's Modulus and Second Moment of Area.

    I know that Young's modulus is a measure of how elastic a material is and is calculated by Stress/Strain.

    I know that the Second Moment of Area can be defined as a objects resistance to bending.

    But if I had a material that had a high Young's Modulus meaning that it was less elastic in other words more stiff then isn't that the same thing as the second moment of area?

    Can anyone see where I am coming from?

    I know the two are related but to me they seem like they are describing the same thing?

    The only difference I can see is that Youngs Modulus describes stiffness in terms of elongation/compressions whereas the second moment of area describes bending/deflecting.

    Can someone explain or define the concepts if I have it wrong?

    Thank you.
  2. jcsd
  3. Nov 2, 2018 #2


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    Young’s modulus E and the second moment of area, I, usually call Area Moment of Inertia, are not at all related. E Is an intrinsic property of the material, while I is a geometric property of the area of its shape. You can have a beam with a high E but a small I , and the beam may not be very stiff at all in bending deflections, like a steel rod for example. The stiffness or rigidity of a beam of a given length is is EI. When both E and I are relatively large, deflections are small compared to low E and low or high I , or low I and hi or low E.
  4. Nov 3, 2018 #3
    thank you.
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