# Pressure and Diving Question

#### verd

Hi,

So I just did a simple ideal gas problem, having to do with a bubble rising from the bottom of a lake... Here's the problem:

A diver named Jacques observes a bubble of air rising from the bottom of a lake (where the absolute pressure is 3.50 atm) to the surface (where the pressure is 1.00 atm). The temperature at the bottom is 4.0 C}, and the temperature at the surface is 23.0 C}.

What is the ratio of the volume of the bubble as it reaches the surface ( V_s) to its volume at the bottom ( V_b)?

Which I got to be 3.74...

Now, I understand what's happening, and I understand the ideal gas law and the concept of pressure. But I am then asked:

Would it be safe for Jacques to hold his breath while ascending from the bottom of the lake to the surface?

Maybe this is common sense, but how do I know if it's safe? I mean, I know that his lungs would be more compressed further underwater, and as he rose, pressure would decrease... But is it safe for him to do this? I mean, it seems safe to me, but I don't know anything about a person's lungs at different levels of pressure... I know that in scuba diving, as you rise, you have to equalize, which is when equalize the pressure in your ears with whatever depth you're at... It would make sense to me that this Jacques character would have to equalize in that manner, but I think they're talking about his lungs, with the reference to the bubble of water...

Thoughts? Am I reading too much into this? Is this safe or not?

Thanks!

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#### Leong

i think it is not safe because his lungs will expand since the volume of the air will increase.

#### verd

right, but where did the air come from? it couldn't have come from the bottom of the lake... wouldn't he have had to inhale at the top and then swim to the bottom?

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