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JEK October 20, 1999 21:23

Please help a high school student! Please
 
Help! How much pressure must a submarine withstand at a depth of 120.0 m? The answer according to my teacher is 1205 kPa, I don't believe her. Your thoughts?

clifford bradford October 20, 1999 23:15

Re: Please help a high school student! Please
 
let's see.hydrostatic pressure is given by: P=rho*g*h so P=1000*10*120 P=1200kPa seems she's right. the numbers are approximate since the density of seawater is over 1000kg/m^3 and g=9.81 but the ballpark is good. believe your teacher.she has a degree.

Glenn Horrocks October 20, 1999 23:16

Re: Please help a high school student! Please
 
Hi,

Your teacher is about right.

pressure = density * g * depth

Where:

density = 1000 kg/m^3 (It's a bit higher for salt water but this will do)

g = 9.8 m/s^2

depth = 120 metres

So the pressure will be 1.2 MPa.

Cheers, Glenn

Md. Ziaul Islam October 21, 1999 11:22

Re: Please help a high school student! Please
 
Dear JFK,

Let me try to explain to you in a very simple way. In this condition, the pressure of a submarine depends upon density, g, and depth. Density of salt water may vary a little bit from place to place in the ocean depending upon the amount of salt dissolved in water. Value of g varies slightly depending upon the distance of the submarine from the center of the earth. In this situation, assuming the value of g and density of salt water constant is a clever approach. So what we have now is the depth of the submarine from the surface of water. Deeper is the location of the submarine from the water surface, higher is the pressure on the submarine and vice versa. Now you can realize that the pressure on the submarine is proportional to the depth keeping the other two parameters (g and density) constant.


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