# Tarzan, Fluids, and Pressure

1. Jan 18, 2005

### Soaring Crane

Ape Man in a movie is shown evading his captors by hiding underwater for many minutes while breathing through a long reed. Assuming the maximum pressure difference lungs can manage and still breathe is -80 mm-Hg , calculate the deepest he could have been.

I immediately thought of P = p*g*h, where p = density. h is the depth, but this is for gauge pressure. Do I use the formula for absolute pressure P = atmospheric pressure + pgh?

Am I correct in my reasoning?

Thanks.

2. Jan 18, 2005

### vincentchan

First... you have to make an assumtion that the lung won't be compress under water, otherwise the problem can't be solve this way.
Yes the absolute pressure under water is $\rho g h + 1atm$... however, the pressure inside the (uncompressed) lung is 1atm... so the DIFFERENT of the pressue is $\rho g h$