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Originally posted by KnifeMissle
This is simply not the issue. You want to use ratios to determine the original volume of water but you can only use ratios if the change in water level is proportional to the change in water volume. If you were to think about the geometry of the barrel, you'd see that this is not the case. Thus, your method is insufficient...
If you knew the volume of the container and the amount of water used to fill the tank, you can simply take the difference and that would be the volume of water oringally in the tank.
However, and again, not only is it a difficult thing to fill a tank with a measured amount of water but you are also disturbing the system. I mean, what's the point of knowing how much water was in the tank if you're going to fill it to find out?
There's much to be said for determining the state of a system without changing it.
The only time I have taken this thread personally is when it became apparent that DDDDave didn't read the thread and that has very little to do with the question and more to do with a peeve of mine.
Instead of defending yourself from criticism, perhaps you should try learning from them?
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First I'll address your bashing of DDDDave. There are plenty of threads around where people didn't read all the responses before responding themselves. There's nothing wrong with it. Although, I'm sure you must read every response to every thread before you respond since it would be ridiculous to criticize someone else if you are guilty on occasion as well, right?
As far as your criticism of my responses, I could care less if you criticize them and I did learn from the criticism and that's the point of a discussion board. Post something, if it doesn't make sense then there's a good chance someone else can help you work your way through it. Of course most try to do it in a constructive rather than arrogant and inflammatory way, but I guess everyone is entitled to their own style.
The original poster never added the criteria that the original condition could not be disturbed. That's simply a requirement you feel compelled to abide by.
I see your point about my method and will modify it to:
Let's say the water depth at the start is 4". Fill the tank to 4" from the top, measuring the amount of fluid added (which can easily be done if you know the rate of flow of the pump you're using and the time spent pumping). Then measure the volume of water needed to fill the remaining 4" of tank. Double it and add it to the volume you added to get the tank to 4" from the top.
And to answer an earlier question of yours:
Quote:
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"Isn't it simpler to just figure out the volume as a function of fluid depth?
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As you pointed out, the method of calculating the volume was already outlined earlier in the thread before my first response. I was simply throwing out a mechanical method of determining it as an alternative. If you don't like it that's fine but you are not the arbiter of what's allowable.