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Simple question about young's modulus

  1. Nov 28, 2012 #1
    I did a practical worked the gradient and calculated E, of a wooden metre rule.

    What I want is a value to compare my value with, I got 5 N/m2

    So 5N will bend the ruler 1m? Seems likely right?
  2. jcsd
  3. Nov 28, 2012 #2

    Simon Bridge

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  4. Nov 28, 2012 #3
    On that page isn't that Mega Pascals?? I got 5Pa
  5. Nov 28, 2012 #4
    and maybe on that page those are MUCH higher maybe cause they calculated it using woods of greater thickness,length, etc.
  6. Nov 28, 2012 #5
    Ohhhh LOL i'm sorry I didn't even see what I typed
    my mind was away. I didn't mean 5 newtons would bend it 1m
  7. Nov 29, 2012 #6

    Simon Bridge

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    Would you get a higher modulus if you used a thicker beam?
    It's a material property. How is the modulus defined?

    You can also look for other people who've done the same and talked about it.
    It's a common enough experiment - done either by vertical deflection by weights or by Timing harmonic motion.
  8. Nov 29, 2012 #7
    I found out my value is very wrong D: I need to recheck my calculations
  9. Nov 29, 2012 #8
    I am so stupid =.= I left off a 10^-8 somewhere in my calculations.

    New value which makes sense NOW is 5.10 x 10^7Pa.
  10. Nov 29, 2012 #9
    Sigh again i was wrong I did it over again I got 5,108.1 MPa
  11. Nov 29, 2012 #10

    Simon Bridge

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    When you have measurements on such a wide variation of scales, it is very easy to misplace lots of zeros :)

    You can see from the discussion of accuracy in the article that these can get very big (as much as 56% it says) so you only need the right order of magnitude. "Conclude: Youngs modulus for a wooded meter-rule was experimentally determined to be _____GPa. This agrees to the same order of magnitude as an accepted value of _____GPa given in ref. ______."

    If you did errors then you can also comment on how good the agreement was.
  12. Nov 30, 2012 #11
    Thank you.
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