On Fri, 27 Jun 2003 11:01:35 -0400, DigitalVinyl wrote:
Repeating Decimal wrote:
in article , David
Hare-Scott at wrote on 6/26/03 4:37 PM:
"Repeating Decimal" wrote in message
...
The five gallon containers for plants always seemed small to me. Today
I got
to measure one of them. When I calculated the volume, it was 3.4
gallons not
five. Am I missing something? Is there a arcane standard for this?
Bill
This seems a large discrepancy even for a container not selling product
by volume. Which gallon (USA or Imperial) does the container use? How
did you do the sums to work out your figure?
David
I used the US gallon which is the smallest on my calculator. I US gallon
is 231 cubic inches.
The formula I derived, although it should be available in reference
books, is:
V = (pi/3)*H*(R^2 +R*r+r^2).
H is the height of the conical frustum representing the shape of the
container. R and r are the upper and lower radii. H= 12 inches. R and r
are each *half* of the diameters 9.75 and 8.5 inches respectively. Out
comes 3.4Gal.
Your formula's correct. I imagine it is mostly blatant marketing
lies...much like the fact that monitors would measure 15" but only be
13.5" while a 19" TV is always 19".
DiGiTAL_ViNYL (no email)
A 19" TV has the same viewing area as a 19" monitor, the convention of
defining a CRT based on the maximum diameter of the tube itself rather
than the actual size of the picture arose with TVs. Once something becomes
an industry standard you can't change it even if it's widely regarded as
wrong. Assuming that the OP is correct and that a 5 gallon pot is really
3.4 gallons then there is probably some rational explanation for this
buried deep in the mists of time. If a pot were cylindrical rather than
conical then maybe a pot with the same diameter as the mouth of the
conical pot would hold 5 rather than 3.4 gallons (I haven't done the
calculation but it feels right). As another poster pointed out, plants are
sold in pots not dirt so their is no fraud involved. Dirt is sold in cubic
feet or yards not in gallons.