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Calculating release speed from distance (Read 126 times)
IronGoober
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Calculating release speed from distance
Nov 17th, 2021 at 10:20pm
 
https://www.desmos.com/calculator/on4xzwtdwz

In the linked calculator, if you fix the ratio of cross-sectional area to mass and the distance traveled is always the same. So, it should be possible to calculate max distance given a certain release speed for a sphere or ellipsoid of any size.

Here, I assume a drag coefficient of 0.1 for the projectile and a spherical shape for simplicity (the Cd should probably be higher).

For a 65 m/s throw, the distance is 340m with a 50g stone and 390m with 50g of lead.
For Larry Bray's throw, the release speed I calculate using this method is ~75 m/s.
It is similar for a 500m throw with 50g of lead.


If you want to calculate it yourself:

For a 50g projectile the ratios are (the ratios change if the mass is changed because area and volume scale differently): this is in kg/m^2

Lead:154 (1.01cm radius)
Granite:59
Basalt:64

Approximately 41 is the optimal release angle with drag.

I included a quick calculator if you want to use your own size/material.
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MassToXsecArea.xls (26 KB | 7 )

John R.
 
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Sarosh
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Re: Calculating release speed from distance
Reply #1 - Nov 24th, 2021 at 5:30am
 
somehow i didnt see this post.
nice calculator
I dont understand the purpose of having different drag coefficients and surface areas for the x and y axis.
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IronGoober
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Re: Calculating release speed from distance
Reply #2 - Nov 24th, 2021 at 9:33am
 
Sarosh wrote on Nov 24th, 2021 at 5:30am:
somehow i didnt see this post.
nice calculator
I dont understand the purpose of having different drag coefficients and surface areas for the x and y axis.

Agreed. It doesn't seem to be that useful of a feature.
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John R.
 
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