How much does a square foot of water weigh?
A square foot of water weighs nothing, technically. 
H[sub]2[/sub]O weighs one kilogram per liter, a liter being 10 cm[sup]3[/sup]. And since it’s your own fault that you’re American, you have to do the rest of the calculations. 
Salt or Fresh? Are you sure you mean square foot?Fresh water is about 62 lbs./Ft[sup]3[/sup] and Salt water is about 64 lbs./Ft[sup]3[/sup]. This is why I wear more lead on my weight belt when diving in salt water than when in fresh. The water I displace has more weight (thus more bouying force).
This is also a “problem” with ships going up river. The water gets shallower and the ship sits lower in the water as the salinity decreases.
A liter is (10 cm)[sup]3[/sup] or 1000 cm[sup]3[/sup].
Well, at 1 gram per cubic centimeter (at 4 degrees centigrade), 2.54 centimeters per inch, 1728 cubic inches per cubic foot, and 2.2 pounds mass per 1000 grams, that gives us about 62 pounds. Which Spritle already said. Damn.
Oh, and if you prefer, that’s justunder 2 slugs. Comparatively, air is 0.002377 slugs per cubic foot at standard temperature and pressure. Sorry, I majored in aeronautical engineering for a couple years, that’s indelibly etched in my mind.
You are quite correct. I was never good at placing the brackets in equations!
Except he asked for weight, not mass…you need to express it in lbf.
D&R…
62 pounds. Got it. None of these Commie liberal metrics for me Thanks.
You can see me put this info to use in the “Is Survivor Fixed” thread David B started in MPSIMS.
But then again, a pint’s a pound, the world around.
Damn! You beat me to it, Spavined!
For rule-of-thumb estimates, a pint weighs a pound, so a gallon of water weighs roughly 8 pounds.
Again, you haven’t dealt with the issue of fresh water or salt water.
[sub](We’ll just see who the commie bastards are around here.)[/sub]
If we are going to branch off into pints, which pints?
An imperial pint, the original measure, is 20 fluid ounces or 0.568 litre, while a US pint is 0.473 litre. So depending where you are your pint of water, pure or otherwise will not weigh the same.
I just did some disturbing calculations.
Assuming a 1.0 gm/cm[sup]3[/sup] density of fresh water, a liter of water has 1 kg of mass.
A liter is 0.2641721 US gallon.
A kilogram is 2.204623 lb-mass.
So, a gallon of water weighs 8.35 lbs.
Can that be right? Given 16 fl. oz./pint, 8 pints/gallon, that means 128 fl. oz. of fresh water weighs 133.6 ounces.
What the hell is the definition of a fluid ounce then?
Even worse, according to Metric & English Unit Conversion the US and Imperial fluid ounces are not the same either!
Seriously, I cannot figure out where these definitions of fluid ounces came from - is it just that ‘ounce’ means ‘one twelfth’ or some such and so there is no relationship between a fluid ounce and an avoirdupois ounce or any other kind of ounce other than an annoying naming coincidence?
Mygod life must be hard being an American.
A fluid ounce is a measure of capacity, not weight.
An ounce is 1/16 of a pound = 437.5 grains = 28.3 g (as any dope buyer would know).
As previously posted one fluid ounce is 1/20 of an imperial pint.
True. In 1828, the British redid their system of liquid measures and defined a gallon as 10 pounds of water at 62[sup]o[/sup]F. The US did not follow suit and kept the old gallon definition of 231 cubic inches. The Imperial pint was set at 20 fluid ounces rather than the old 16, which kept the sizes of the two fl. oz. close but not exact. (And makes the “pint’s a pound the world around” maxim wrong, at least for the “world around” part.) The US fluid ounce is 29.573 ml and the Imperial fluid ounce is 28.412 ml.
This is true, but the numbers are close enough that it seems reasonable to suppose that a fluid ounce was originally intended to represent the volume occupied by one ounce of water.
Given that the density of water changes with temperature (and really slightly with pressure), and that the definition of the ounce (in the US) has apparently mutated over the years, it’s still not that far off. Certainly good enough for back-of-the-napkin calculations. I usually use 8 pounds/gallon when I estimate stuff - it’s easy to remember, and is pretty close.
My edition of Eshbach’s Handbook of Engineering Fundamentals gives water as having a density of 1.936 slugs per cubic foot at 68[sup]o[/sup] F and 1 atmosphere pressure. (A rant: I hate slugs! The pound-mass is much more convenient: 1 lbm = .00311 slug, and is equal to the amount of mass that weighs one pound-force under 1 G)
Anyway, 1.936 slugs/ft[sup]3[/sup] is [ul][]997.8 kg/m[sup]3[/sup][]0.9978 g/cm[sup]3[/sup][]62.29 lbm/ft[sup]3[/sup][]8.327 lbm/gal[]1.041 ounces/fluid ounce (US)[]1.000 ounces/fluid ounce (Imperial)[/ul]assuming I did the conversions correctly.
Now I can get really cool, I can quote facts that make no sense to me at all.
Figure this out - in the US a liquid pint is equal to 0.473 litre while a dry pint is equal to 0.550 litre.
It’s a laugh a minute, isn’t it??
Nobody seems to have mentioned (or did I just miss it?) that a litre of water weighs exactly a kilogram (at STP)
and (In the UK at least) “A pint of water weighs a pound and a quarter”
I would just like to say that if this thread isn’t proof that we all need to switch to metric, nothing is going to convince you guys. 