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Q & A: Aquarium safety

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Most recent answer: 10/22/2007
Q:
how thick would a glass for an aquarium of 2m high and 4m long and 3 m wide would be?
- mohammed nabaa (age 15)
british council realated school, saudi arabia,jeddah
A:
Well, we cannot vouch for different kinds of glasses. Some break more easily than others, and some are less brittle. If a piece of glass already has a crack in it, the crack will grow over time and weaken the glass. Water only makes this worse -- water molecules can get inside a crack in glass and speed the growth of the crack. A good rule of thumb is that it's best to make the glass too thick than too thin. Better safe than sorry, we always say!

What we can help you with is how much pressure there is at the bottom of your tank. The pressure of water in the tank will be rho*g*h at a depth h from the top. Add to that one atmosphere of air pressure, and subtract it again because there's one atmosphere of air pressure on the other side of the glass. rho is the density of water, 1000 kg per cubic meter, and g is the acceleration of gravity, 9.81 meters/second**2. h is measured in meters, and the pressure will then be in Pascals.

One suggestion for making a strong tank that is very large is to use acrylic plastic instead of glass. Lucite, for example, is very strong, very transparent, and resists cracking. Many of the very large aquariums use acrylic plastic windows instead of glass.

Tom

(published on 10/22/2007)

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