physics question that I dont understand?

Question

In a movie, Tarzan evades his captors by hiding underwater for many minutes while breathing through a long, thin reed. Assuming the maximum pressure difference his lungs can manage and still breathe is -72 mm Hg, calculate the deepest he could have been

Answer 1

♣ proportion: 760 ↔ 10^5 N/m^2 is atmospheric pressure;
72 ↔ p is critical pressure on his chest from water;
thence p = 72*10^5/760 = 0.095·10^5 N/m^2;
now water density w=1000 kg/m^3;
then p=d*w*g, where d*w is mass of water column d meters deep,
hence depth d=p/(wg) = 0.095·10^5/(1000*9.8) = 0.97 m;

Answer 2

The question is a bit bogus, because the length of the tube becomes problematic, but I think what the question is really asking is at what depth is the water pressure 72mm Hg which is the maximum pressure his chest muscles could overcome.

Hopefully, they gave you some other info, like what the pressure was at the level of the water. At sea level it is, 1013.25 mm so adding 72 to it gives about 1085.25 mm
so running it through the formula that they should have given you, you should come up with a depth of about .7342 meters.

Answer 3

It's easy to figure out if you consider that the specific gravity of mercury is 13.546. Thus, the greatest depth he could breath under water is 13.546*72 mm = 975.31 mm under the surface of the water.

You don't need to worry about the exact absolute pressure of the atmosphere, since it would be pressing on the air in the reed and on the surface of the water -- and hence on his lungs through the incompressible fluid -- in exactly the same way. Thus you can neglect it and assume they mean 72mm Hg in GAGE pressure, not ABSOLUTE pressure.

Answer 4

depends on the rigidity of the reed (quality contol) and the pressure of the water which will increase as you go deeper. as i recall he was abt 1 M down, with a reed of 0.375 ID he could be there for quit a bit. thats why divers lines are under pressure, and somewhat rigid. also the air (not oxygen) is filtered. deep divers use internally pressurized suits, it's a science that started evolving in the later 1800's. not to well understood in the day of the CSS Hunley....

Answer 5

It' look which you're no longer getting pastime in Physics. First attempt to get pastime. i think of straight forward way so you might keep in mind formulation is which you would be able to write the formulation on a place on your analyzing room so as which you would be able to keep a watch on that each and each physique time..with regard to the conversion of CGS and SI you may desire to take help of length analysis. ..

Answer 6

Water pressure is 62.4 lb per cu-ft/144sq.in = 0.433 psi/foot of depth.

72mm of mercury = 1.392 psi

1.392psi/.433 psi/foot of depth = 3.2147 feet = 980.54mm

Answer 7

ummm, it needs some calculations..
i'll get back to you in a while.

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