Hydraulics and Fluid Mechanics in ME
The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)

(p/W) × (a/A)
(p/W) × (A/a)
(W/p) × (A/a)
(W/p) × (a/A)

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Hydraulics and Fluid Mechanics in ME
For similarity, in addition to models being geometrically similar to prototype, the following in both cases should also be equal

all the four ratios of inertial force to force due to viscosity, gravitation, surface tension, and elasticity
ratio of inertial force to force due to gravitation
ratio of inertial force to force due to viscosity
ratio of inertial force to force due to surface tension

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Hydraulics and Fluid Mechanics in ME
Froude number is significant in

Simultaneous motion through two fluids where there is a surface of discontinuity, gravity forces, and wave making effect, as with ship's hulls
Supersonics, as with projectile and jet propulsion
All of the listed here
Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.

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