MadSci Network: Physics

Subject: effect of air pressure on water pressure

Date: Mon Jul 21 00:42:34 2003
Posted by Jason
Grade level: grad (science) School: No school entered.
City: Wakefield State/Province: Yorkshire Country: UK
Area of science: Physics
ID: 1058766154.Ph

If i measure the water pressure in a swimming pool at a certain depth, i am 
told in text books that the pressure is only related to depth, therefore 
pressure = density * gravity * height + air pressure above the pool.

now here is my problem.
If i now slide a solid horizontal sheet of steel partly across the surface of 
the water to prevent any air from interacting with the pool surface and the 
steel is supported at the pool side.
I find it hard to believe that the pressure under the steel is d * g * h
but in the rest of the pool it is d * g * h + air pressure.
please let me know what i am missing here.

one more please
i upturn a drinking glass in water, raise the glass until the rim of the glass 
is still in the water, therefore the glass is full of water.
is water pressure under the glass density * gravity * height (i.e. no air 

Thanks for your time
Jason Bloomfield

I think text book explanations should be clearer

Re: effect of air pressure on water pressure

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