CALCULATION OF PRESSURE

I think your question became truncated somewhat!!

If you mean you need to know the pressure in a hydraulic piston to lift 500kg...

Then its simply the cross sectional area of the piston you need to know...

If the piston were 1 cm^2 then you would need a pressure of at least 500 / 1 = 500 kg/cm^2...

Or if Masu is around and wanting his force units!

It would roughly be 5000 N/cm^2..

John.

v need it 4 both.....i think the same method will be followed in pneumatics also.......

Yes, it's just basic pressure definition:

P = F x A where, using SI:

P = pressure [Pa, or N/m2]

F = force [N]

A = area [m2]

Any specific problem with it?

The only difference between hydraulics and pneumatics is that air is compressible, and you'd normally use far lower pressures, larger areas, but frequently higher speeds.