Metmom. I have to disagree because of the specificity of "immersion" meaning completely submerged. Weight can only be determined IF the body is floating in the medium... immersion can only measure volume accurately.
Take for example a 1 Meter cube of lead and a 1 Meter cube of styrofoam. Both occupy the same volume... but the cube of lead is really easy to immerse in water while you have to work really hard to immerse the cube of styrofoam.
A cubic centimeter of water is very close to 1 g/cc in weight, so a cubic meter of water would weigh 1000 Kilograms or about 2200 pounds. A cubic centimeter of lead weighs ~11.3 grams so the cubic meter of lead would weigh 11,300 Kilograms, or almost 25,000 pounds ... yet it would displace only 1000 Kilograms (2200 lbs) of water. A cubic meter of average density Styrofoam would weigh about 100 Kilograms (220 lbs) (Styrofoam is sold in densities from 25 to 200 Kilogram per cubic meter). That cube of styrofoam, when floated in water, would only displace 100 Kilograms of water... you would have to apply at least 900 Kilograms of force to submerge it.
Displacement of an object that will float measures weight. The displacement of a submerged object can only provide information about volume.
Thanks.
You don't need to immerse a human body in water to get weight. There are much simpler ways to measure weight.
The fact that this procedure uses immersion is a pretty good indicator that the needed variable is volume.
I see.
The original comment from tpanther in post 760 was this...
"Of course, sometimes a person is suspended in a tank of water and the amount of water displaced measures body weight/mass/fat content, muscle content, etc."
Note: he said *suspended*.
Which is what started this all.
In post 763 js replied with....
You are not measuring weight, nor mass, nor fat content.
In post 766 js changes the term from *suspended* to *immersed*, thus changing the direction of the debate.
Humor me. show me a link to a claim that the water displaced by an immersed human body measures weight, mass and body fat.
Post 780-js
You made the rather interesting claim that the displacement of water by a human body measures weight and fat content rather than volume, and you think I'm absurd?
post 789-js:Displacement measures volume, not weight.
post 793-js When you say “immersed” do you mean completely immersed, or floating? I’m assuming you mean completely immersed.
tpanther never said *immersed*. That was js' statement.
In post 795 js:It remains true that measuring the amount of water displaced by a completely immersed object tells you its volume and tells you nothing about its weight.
The whole immersion thing was a construct. It was not brought up by tpanther. Why js is arguing against someone for something they never said is beyond me.
Displacement of an object that will float measures weight. The displacement of a submerged object can only provide information about volume.
Which was never ever the point in the first place. The entire reason for the procedure is to get an idea of what a person’s body fat percentage is. Measuring volume is but one of the steps, the final step in the calculations is geting the body fat MASS percentage.
js would know this if he simply took the time to digest what he reads.