# Hydraulic lift

Discussion in 'MCAT Study Question Q&A' started by mejorization, Jul 28, 2011.

1. ### mejorization 7+ Year Member

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In a hydraulic lift, do the two pistons have to be at the same height? It seems like it would because of Pascal's law.

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2. ### tn4596 5+ Year Member

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I don t think so...I made one with unbalanced piston...
not sure how u get that from pascal law

3. ### Majik

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No, they do not depend on height whatsoever. If you were asking this because you thought gravity is somehow involved, well that's not true.

Pascal's Law says that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same.

When you apply a force on a piston, over a given area (the area of the piston), you are exerting a pressure on that piston. We can take advantage of this fact and Pascal's law to increase our force output by increasing the area since:

P1 = P2

so if we increased the area by a factor of 10, then:

F1/A1 = F2/A2
10 A2 x (F1/A1) = F2,

Force must increase by a factor of 10.

Also it's worth knowing that the density of the solution does not effect Pascal's Law since it's doesn't affect the applied pressure. Remember, the force is due to some external force like an engine or human (not gravity!). All that's needed is a fluid, any fluid and the same pressure will result each time!

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