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| Sectional Density http://ellegon.com/forum/viewtopic.php?f=6&t=9387 |
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| Author: | KonaSeven [ Sat Jul 12, 2008 8:24 am ] |
| Post subject: | Sectional Density |
Why does the shooting industry/sport calculate sectional density different than classical physics? Whereas the SD of a given object is generally calculated by dividing the mass of the object by the cross section area. Determined by the orientation of the view. In bullets I often see it determined by dividing the weight of the bullet in pounds by the diameter^2 in inches. The weight vs mass conflict I can accept. (Grudgingly) Since most bullets will be used on or near the surface of the Earth. But, why change from the cross sectional area (pi*r^2) to D^2. TIA |
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| Author: | KonaSeven [ Sat Jul 12, 2008 8:46 am ] |
| Post subject: | |
Follow-up note: A Wiki article will invariably come up while doing a search. This one is most curious. It uses a conventional physics formula in its body, but cites a Chuck Hawks article as it's source. Yet, Chuck Hawks uses the bullet type formula, unlike the formula in the text. 
I think the bullet formula was invented as a convenient way to compare calibers and masses of bullets. It really has nothing to do with the actual sectional density. |
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| Author: | Tick Slayer [ Sat Jul 12, 2008 4:11 pm ] |
| Post subject: | |
I saw the title of this thread and perked up. "Hey!" I thought, "I'm not the only one in the group who knows about sectional density." ...Until Kona started reeling off formulas. Then it sort of changed to, "Erm. I thought I knew about sectional density, but really I just know that 1) it's generally good and 2) how to get more in a few circumstances." 
Sorry, Kona. Can't help you there. Math makes my eyeballs spin and shuts down my brain. |
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| Author: | KonaSeven [ Sat Jul 12, 2008 4:53 pm ] |
| Post subject: | |
 That's okay!! It keeps me in a job teaching others.
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