randlemcmurphy
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For our coursework we were told the practical will be about a loaded metre rule (its deflection) and its oscillations. In preparation I looked over notes and found online a formula that says the deflection is directly proportional to the length of the rule cubed. This has completely baffled me as to why this is so. I assume the practical won't go into this much detail, however I am rather intrigued as to why this is so.

Thanks.
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Smaug123
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(Original post by randlemcmurphy)
For our coursework we were told the practical will be about a loaded metre rule (its deflection) and its oscillations. In preparation I looked over notes and found online a formula that says the deflection is directly proportional to the length of the rule cubed. This has completely baffled me as to why this is so. I assume the practical won't go into this much detail, however I am rather intrigued as to why this is so.

Thanks.
What's the source of that formula? It seems unlikely to me on dimensional grounds (deflection is in metres, length^3 is in m^3).
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pleasedtobeatyou
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(Original post by randlemcmurphy)
For our coursework we were told the practical will be about a loaded metre rule (its deflection) and its oscillations. In preparation I looked over notes and found online a formula that says the deflection is directly proportional to the length of the rule cubed. This has completely baffled me as to why this is so. I assume the practical won't go into this much detail, however I am rather intrigued as to why this is so.

Thanks.
Its great you have that much interest but unfortunately the complete explanation for this would take too long.

In short, you model the ruler as a beam and apply equations from beam theory to it. It's then possible to formulate an equation for the oscillatory behaviour of the beam as it vibrates.

If your source is reliable, the equation will show that the deflection is proportional to the length of the beam/ruler cubed.

Hope this helped.
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pleasedtobeatyou
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(Original post by randlemcmurphy)
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(Original post by Smaug123)
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Actually, it's much more simple than I thought. I'm assuming you're performing an experiment where you have one end of the ruler fixed as a cantilever beam.

http://www.clag.org.uk/beam.html

About halfway down the page, you can see the equation. A full derivation is very lengthy. You would need to know all the basic beam theory before you could get to this stage.

So, it's not worth it
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