Is 5 N/m² a Reasonable Young's Modulus for Wood?

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SUMMARY

The discussion centers on the determination of Young's Modulus for wood, specifically a wooden meter rule, with an initial erroneous value of 5 N/m². After recalculating, the corrected Young's Modulus is found to be approximately 5,108.1 MPa, which aligns with accepted values in the literature. The conversation highlights the importance of accuracy in measurements and the potential for significant errors when dealing with varying scales. It emphasizes that Young's Modulus is a material property and can vary based on the dimensions of the sample used.

PREREQUISITES
  • Understanding of Young's Modulus and its significance in material science
  • Familiarity with basic mechanics and material properties
  • Knowledge of measurement techniques such as vertical deflection and harmonic motion
  • Ability to perform dimensional analysis and error checking in calculations
NEXT STEPS
  • Research the calculation methods for Young's Modulus in different materials
  • Explore the impact of sample dimensions on material properties
  • Learn about common experimental errors in mechanical testing
  • Investigate accepted values of Young's Modulus for various wood types
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Students and professionals in materials science, mechanical engineering, and woodworking who are interested in understanding the mechanical properties of wood and the experimental determination of Young's Modulus.

lionely
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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?
 
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On that page isn't that Mega Pascals?? I got 5Pa
 
and maybe on that page those are MUCH higher maybe cause they calculated it using woods of greater thickness,length, etc.
 
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
 
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.
 
I found out my value is very wrong D: I need to recheck my calculations
 
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.
 
Sigh again i was wrong I did it over again I got 5,108.1 MPa
 
  • #10
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.
 
  • #11
Thank you.
 

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