# The Naked Scientists Forum

### Author Topic: What determines water pressure?  (Read 1478 times)

#### thedoc

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##### What determines water pressure?
« on: 17/01/2014 15:30:02 »

I have a fundamental confusion about the physics of water pressure.

If I understand it correctly, the pressure of a given tank of a water is solely dependent on the height, not the width of the tank? Therefore, a thin column of water would have the same pressure coming out at the bottom as would a wide one? Does the volume of the water make any difference? And how does one explain the difference in pressure when one widens or narrows the aperature where the water is coming out?

Thanks so much for your help.
Love the show!

What do you think?
« Last Edit: 17/01/2014 15:30:02 by _system »

#### CliffordK

• Neilep Level Member
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##### Re: What determines water pressure?
« Reply #1 on: 17/01/2014 18:34:13 »
Pressure can be achieved either by using a column of water, or a mechanical pressure device such as a pressurized air bladder in a tank.

For a static system, the size of the water column is unimportant, only the height.

However, for flow, more water can flow through a larger pipe.  Lower flow through restrictions of pipe sizes can seem like lower pressure.

Also note, the pressure is usually measured in weight per area such as pounds per square inch (PSI).  The larger the opening, the more area, and more weight for that area.

#### evan_au

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##### Re: What determines water pressure?
« Reply #2 on: 18/01/2014 11:26:16 »
Blaise Pascal is reputed to have performed an experiment where he burst a wooden wine barrel by pouring water into a thin tube.
http://en.wikipedia.org/wiki/Pascal%27s_barrel

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##### Re: What determines water pressure?
« Reply #2 on: 18/01/2014 11:26:16 »