Re: I need someone's brain juice here?


Joe Fischer wrote:
> On 30 Dec 2005 13:18:27 -0800, guskz@xxxxxxxxxxx wrote:
>
> >Slightly off topic but the other newsgroups aren't as read....
> >
> >Here's two web links on two widely understood fluid pressure models:
> >
> >http://hyperphysics.phy-astr.gsu.edu/hbase/pman.html#meac
> >
> >http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html#hpress
> >
> >
> >Both are related to vertical pressure (or Force / Area = pressure) on a
> >fluid, yet both use 2 completely different equations to calculate the
> >fluid's vertical travel distance.
>
> The first one relates to static atmospheric pressure
> used in pressure gauges some of which use mercury or
> air, a complete vacuum will lift mercury about 30 inches,
> and will lift water about 30 feet.
> The second one is more like hydraulic presses
> or cylinders where oil is pumped under higher pressures
> to do work.
>
> >One use's the fluid's density the other simply says Work1 = Work2 thus
> >F1*D1 = F2*D2
> > (or P1*A1*D1 = P2*A2*D2) where as the other says P1 = density * H *
> >gravity + P2
> >
> >If you look at both models you'll notice that H = D1+D2
> >
> >Anyone with enough brain juice to tell me why the difference, I can't
> >figure it out since both models simply practically the same????
>
> The first one has atmospheric pressure only to
> change the level of the fluid.
>
> The second one uses mechanical advantage by
> having the pump piston diameter to be smaller than
> the working cylinder piston diameter.
>
> Joe Fischer

Tks Joe, actually the first one (other than the mercury model) has two
pressures P1 and P2 and not nescessarily atmospheric pressure.

.

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