I apologise for the very basic question, I’m just trying to grasp the concept of Pascal's law.

I’m familiar with the fact that if pressure is applied to a confined liquid, the latter will be applied equally throughout the fluid, but what would happen if pressure is applied by two pistons at the same time rather than just one causing the second to move. If two pistons with a surface area of $10\ m^2$ applied force of $10\ N$, what would be the increase in pressure throughout the liquid? Would each piston deliver $1\ Pa$ of pressure each, with the overall increase throughout the fluid being $2\ Pa$. If this is not the case, why not?

Would one piston of $3\ m^2$ with $3\ N$ pushing on it apply less pressure than two of 2 square meters with two newtons and 1 of 1 square meter with one newton.

3 / 3 = 1 pascal change

2/2 + 1/1 = 2 pascal pressure change.



1 Answer 1


Consider any piston in your system. If the system is in equilibrium the net force on the piston must be zero, so if we apply a force $F$ to the piston and the pressure is $P$ and the piston area $A$ we must have:

$$ F = PA $$

If the system is in equilibrium this has to be obeyed by all the pistons in your system regardless of their area.


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