Quiz - Physics - Volume at Depth

[tridacna]

Am I correct in this is what you must do if it's to be a depth that is not exactly 2 ata or 4 ata, etc.--like "what will the volume be at 46 fsw"? I suppose if you were a genius with numbers you may do it in your head.

If you convert to metric, no genius necessary.

 

[TMHeimer]

If you convert to metric, no genius necessary.

Don't know about that. "What will the volume be if you take it to 12 meters"? Same problem, no? 12 meters is not a "round number" like 10 or 20 meters (1, 2 ata).

 

[Angelo Farina]

Don't know about that. "What will the volume be if you take it to 12 meters"? Same problem, no? 12 meters is not a "round number" like 10 or 20 meters (1, 2 ata).

At 12 meters the pressure is 2.2 ATA.
So 1 liter at 12 meters will become 2.2 liters at surface. No calculator required, with metric units you can do it easily in your brain.

 

[tridacna]

Don't know about that. "What will the volume be if you take it to 12 meters"? Same problem, no? 12 meters is not a "round number" like 10 or 20 meters (1, 2 ata).

You answered your own question. (Almost). Metric truly is simple.

 

[Storker]

One way to do this kind of problem is to break it into two parts: first take the object to the surface, then as a new problem take that volume back down to the final depth.

Another way is to remember that P1V1 = P2V2. Simple as that.

 

[TMHeimer]

At 12 meters the pressure is 2.2 ATA.
So 1 liter at 12 meters will become 2.2 liters at surface. No calculator required, with metric units you can do it easily in your brain.

Yes, but how do you know 12 meters is 2.2 ATA? You obviously know that 10 meters is 2 ATA, 20 meters is 3 ATA-- like 33 feet & 66 feet imperial.
You don't know what 37 feet is, just like you don't know what 17 meters is-- unless you do calculations or actually have these figures memorized.

I think I now follow you--
So, 12 meter is 2.2 ATA because you know that 10 meters is 2 ATA then just add the .2.--= 2.2 ATA.
With 17 meters, 10 meters is 2 ATA then just add the .7. -- = 2.7 ATA.
Am I correct? If so, I see how it's easier than imperial.

 

[Storker]

how do you know 12 meters is 2.2 ATA?

Because we know that 10 meters is roughly 1 AtmG, 15 meters is roughly 1.5 AtmG and 20 meters is roughly 2 AtmG. And ATA = AtmG + 1.

 

[BlueTrin]

Yes, but how do you know 12 meters is 2.2 ATA? You obviously know that 10 meters is 2 ATA, 20 meters is 3 ATA-- like 33 feet & 66 feet imperial.
You don't know what 37 feet is, just like you don't know what 17 meters is-- unless you do calculations or actually have these figures memorized.

I think I now follow you--
So, 12 meter is 2.2 ATA because you know that 10 meters is 2 ATA then just add the .2.--= 2.2 ATA.
With 17 meters, 10 meters is 2 ATA then just add the .7. -- = 2.7 ATA.
Am I correct? If so, I see how it's easier than imperial.

You just divide by ten and add 1.

But yea your method is the way one can remember easily in a pinch.

 

[Angelo Farina]

Yes, but how do you know 12 meters is 2.2 ATA? You obviously know that 10 meters is 2 ATA, 20 meters is 3 ATA-- like 33 feet & 66 feet imperial.
You don't know what 37 feet is, just like you don't know what 17 meters is-- unless you do calculations or actually have these figures memorized.

I think I now follow you--
So, 12 meter is 2.2 ATA because you know that 10 meters is 2 ATA then just add the .2.--= 2.2 ATA.
With 17 meters, 10 meters is 2 ATA then just add the .7. -- = 2.7 ATA.
Am I correct? If so, I see how it's easier than imperial.

Exactly, you are correct. I can give you the pressure in bar at any depth in meters. I just divide by 10, then add 1 (the atmospheric pressure).
Please consider that in SI the following approximate equalities are explicitly declared to be acceptable:
1 bar = 1 ata = 1 kgf/cm2 = 10m of water column.
This makes life much easier...

 

[TMHeimer]

I misread and voted wrong--what happened to the "change vote" option?