Quiz - Physics - Partial Pressure of Nitrogen

If an air filled balloon is taken to a depth of 20m/66ft, what is the approximate partial pressure o

  • a. .8 ATA/12 psi

  • b. 1.6 ATA/23 psi

  • c. 2.4 ATA/35 psi

  • d. The answer cannot be determined from the information given.


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As a pedant I'm wondering why the metric answer uses the non-metric unit of ata, rather than bar.
??? 1 bar is approximately 1 ata - SI includes tolerances, and its formally established that this equivalence is allowed.
As saying that the gravity acceleration is 10 m/s2 instead of 9.81 m/s2: or saying that a mass of 1 kg weights 10 Newtons (instead of 9.81 Newtons).
This kind of approximation is built in inside the SI, and is a good way of remembering users that no calculation is ever "exact"....
 
Oh, I'm not disputing the value. If the answer given were 2.4 bar I'd think that's fine, and sufficient precision for the purpose. The only silly thing is that the "metric" answer was 2.4 ata, when ata is not a metric unit.
 
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I'd argue that it is a "system in-specific" reference physical constant. Just like the freezing and boiling points of water, etc.

3 ATA = 3 * Standard sea-level atmospheric pressure.

3 FPW = 3 Freezing point of (fresh) water at 1 ATA.
 
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