settle a dispute

r90s · Post by **r90s** » Sat Oct 08, 2011 10:57 am

Anyone try to prove it yet?

Because I just did:

And here is what happened:

http://www.youtube.com/watch?v=TQ3rL-2u ... rofilepage

The two lengths of tubing showed a difference in pressure as indicated by the movement of the water in the loop.

Cheers,
Jon-Lars

robert · Post by **robert** » Sat Oct 08, 2011 1:58 pm

I just did the same test with mercury sticks and the levels were even.

dougie · Post by **dougie** » Sat Oct 08, 2011 2:12 pm

Pressure = force per unit of area which only depends on the internal diameter of the hose.
It does not depend on the volume of the hose, which is also determined by its length.
In this case vacuum is negative pressure, but the same rule applies.

r90s · Post by **r90s** » Sat Oct 08, 2011 2:58 pm

Boyle's law:

P1V1 = P2V2

Major Softie · Post by **Major Softie** » Sat Oct 08, 2011 3:08 pm

r90s wrote:Anyone try to prove it yet?
Because I just did:
The two lengths of tubing showed a difference in pressure as indicated by the movement of the water in the loop.
Cheers,
Jon-Lars

robert wrote:I just did the same test with mercury sticks and the levels were even.

LOL!!!

This makes the title of this thread even more ironic.

Major Softie · Post by **Major Softie** » Sat Oct 08, 2011 3:10 pm

Rob Frankham wrote:
Major Softie wrote:You do realize that, if this were true, no vacuum gauge in the universe could work accurately unless designed only for one length of tubing.
If this comment is in reponse top my previous post, then no, I don't realise that... in fact I'd really like to know how you get that from what I said.

Rob

Sorry, Rob, no. It was to r90s. I should have been more clear.

robert · Post by **robert** » Sat Oct 08, 2011 3:23 pm

The mercury sticks are open to atmosphere. Your closed system is just moving the liquid from one side to the other.

r90s · Post by **r90s** » Sat Oct 08, 2011 3:55 pm

..which shows that the two lengths of hose have different pressures.

Mercury won't show enough movement to be visible to a naked eye - it's too heavy.

I can't do much more here. Study up and give us the math and references to explain your statements. Make a video, post some photos.

I did.

Jon-Lars
Bevrly, WA

George Ryals · Post by **George Ryals** » Sat Oct 08, 2011 4:42 pm

r90s, when you plumb the long and short tubes together with a tee, they become one tube. One tube, one pressure and one height in both tubes. The only way to have different liquid heights is to have different pressures on top of the liquid in each tube.

dougie · Post by **dougie** » Sat Oct 08, 2011 4:44 pm

Where's StephenB?
We need StephenB here.
Hey Stephen

Boxerworks.com

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