# water pressure question

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#1
if you were to press down on the disk on one side, why does the disk on the other side rise? like whats the reason, in terms of pressure, for that to happen? Why does the volume of water below that disk decrease? cant find an answer to this specifically...

many thanks
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5 months ago
#2
I guess it's supposed to be a closed hydraulic system filled with an incompressible liquid.

The volume of the incompressible liquid has to remain constant because it can't be compressed and can't escape... So if one piston goes down the other has to go up
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#3
(Original post by Joinedup)
I guess it's supposed to be a closed hydraulic system filled with an incompressible liquid.

The volume of the incompressible liquid has to remain constant because it can't be compressed and can't escape... So if one piston goes down the other has to go up
this sounds stupid but why does the piston go down? when the piston goes down, the volume of water below it decreases, so the pressure of the water on the disk decreases? is that correct? xx
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5 months ago
#4
(Original post by Qxi.xli)
this sounds stupid but why does the piston go down? when the piston goes down, the volume of water below it decreases, so the pressure of the water on the disk decreases? is that correct? xx
The pressure is just force per unit cross sectional area

The small disk has mass 1kg and cross sectional area 1... 1/1 is 1 so the pressure is one
The big disk has twice the mass and twice the area ... 2/2 is 1 so the pressure is one

it should be in equilibrium IMO
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