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Unread 09-01-2006, 14:31
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Re: Calculating Angle to fire at

Quote:
Originally Posted by Kevin Watson
Hmmm, while we're picking nits, is your assumption that Cd = 0.5 a good one? 0.5 is worst case for a smooth sphere with perfect laminar flow over the surface. These balls are more like golf balls, which produce quite a bit of turbulence behind them, which can drop the Cd by at least half. Also, your drag force assumes a constant velocity. Is this really the case?

I guess I should have said that the effects of wind resistance should be ignored. Discussing drag coefficients and the Reynold's number of a nerf basketball is silly and will only serve to confuse people, who might get turned-off to the idea of going for the three point score.

-Kevin
I will grant you all those points. I didn't really want to pull out my fluid dynamics book or anything. I've got a quick and dirty spreadsheet I'll be posting later tonight to help out any teams lacking in physics. I'll probably settle on a .25 Cd as a good compromise, .5 was just the first that popped to mind. It should give teams a second more conservative datapoint to judge from.

Edit: Predictably, 12 m/s puts the Reynold's number right in the critical range for a rough sphere where Cd drops a ton depending on the roughness of the sphere. At 10 m/s the Cd is comfortably 0.5 for most roughnesses. So go figure. It's still an estimate, but it will err on the side of shorter than reality.
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Last edited by Kevin Sevcik : 09-01-2006 at 15:26.