suction with fluids 1

[stodge45]

I have a piston inside a cylinder. The cylinder has no end on it and the piston is level with the top of it. The area of the piston is 1 square inch. If I put my hand over the top of the cylinder and draw the piston down I will immeadiately be creating a total vacuum. Am I right in thinking that no matter how far I retract the piston there will only ever 14.7 LBS of force on my hand? Will there become a point at which a neat cylinder of my hand gets 'sucked' into the cylinder?

 

[budt]

The highest possible pressure your hand will see is One Atmosphere pressure wherever you happen to be doing the experiment. At Sea Level on an average pressure day you would have 14.7 PSI. Otherwise pressure will be the Barometer reading for that location.

On a Space Shuttle flight in the open cargo bay you would not feel anything since there is no atmosphere at its orbit altitude.

In Death Valley the pressure would be higher than at Sea Level since there is more depth of atmosphere.

Whether that pressure on one square inch would cause your flesh to be pushed into the cylinder would depend on how tough your flesh is. Notice I said pushed since it is Atmospheric Pressure from the outside that is pushing in.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING