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Archimedes' Law

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The Pressure Under Water

The Pressure Under Water

Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class Christopher Perez
Source: http://commons.wikimedia.org/wiki/File:Navy_Diver5.jpg
License: CC BY-NC 3.0

A deep sea navy diver in the picture above searches the crash site of a WWII military aircraft near Palau. These deep sea divers are exposed to a tremendous amount of pressure, and without their protective gear, they would not be able to survive. For every meter they descend, the pressure increases by nearly 10,000 pascals!

Amazing But True

• The pressure felt by deep sea divers is due to water being incompressible. In other words, you can?t squeeze water. The further you are under the surface of a body of water, the more water there is on top of you. Imagine the water was replaced with concrete. You can easily see that as you descend, the amount of concrete between you and the surface increases. With more concrete or water above you, there is more weight pressing down on you.

Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class Christopher Perez
Source: http://commons.wikimedia.org/wiki/File:Navy_Diver6.jpg
License: CC BY-NC 3.0

Water pressure changes as the diver swims deeper into the sea [Figure2]

• This principle of the transmission of fluid pressure is the basis for Pascal?s law. Mathematically, the change in pressure of an enclosed fluid is equally transmitted to all points in a fluid. The following equation is referred to as Pascal's law:

$\triangle P = \rho g \triangle h$

Can You Apply It?

Using the information provided above, answer the following questions.

1. While underwater, you swim 10 meters to the left of your current position without changing your vertical displacement. How much has the pressure on your body changed by?
2. What are the units of Pascals made of?
3. If you were to dive 10 meters below the surface of the Earth, how many times greater would the pressure on your body be?

1. [1]^ Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class Christopher Perez; Source: http://commons.wikimedia.org/wiki/File:Navy_Diver5.jpg; License: CC BY-NC 3.0
2. [2]^ Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class Christopher Perez; Source: http://commons.wikimedia.org/wiki/File:Navy_Diver6.jpg; License: CC BY-NC 3.0

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