Pressure vs. Vacuums

irisher · Fri Jun 17, 2011 2:09 pm

Atm means atmosphere. It is equivalent to 14.7 .

Tobin · Fri Jun 17, 2011 2:15 pm

irisher wrote:Atm means atmosphere. It is equivalent to 14.7 .

Yepp, but i thought atm was only a old swedish abbreviation that were replaced by bar. Ive got atm printed on the old tubes at home and bar on the newer ones.

saefroch · Fri Jun 17, 2011 2:19 pm

Tobin wrote:
irisher wrote:Atm means atmosphere. It is equivalent to 14.7 .
Yepp, but i thought atm was only a old swedish abbreviation that were replaced by bar. Ive got atm printed on the old tubes at home and bar on the newer ones.

That's very odd. The used to measure most pressures in atmospheres?

Tobin · Fri Jun 17, 2011 3:42 pm

saefroch wrote:
Tobin wrote:
irisher wrote:Atm means atmosphere. It is equivalent to 14.7 .
Yepp, but i thought atm was only a old swedish abbreviation that were replaced by bar. Ive got atm printed on the old tubes at home and bar on the newer ones.
That's very odd. The used to measure most pressures in atmospheres?

I dont know, have only seen "atm" at my old propane tubes and other tubes. Therefore i thought it was some old swedish name for bar. Now i know better

Technician1002 · Fri Jun 17, 2011 5:28 pm

Atm is relative and is poorly defined as barometric pressure varies with location, temperature, altitude, and weather.

Bar on the other hand is an absolute measurement and defined.
http://en.wikipedia.org/wiki/Bar_%28unit%29

Pascal and Torr is also defined.
http://en.wikipedia.org/wiki/Pressure

Here is info on how it is measured. Some are absolute measurements referenced to a vacuum and others are relative referenced to local atmospheric pressure.
http://en.wikipedia.org/wiki/Pressure_measurement

As far as the broken youtube link in the video, a simple youtube search brings up several great examples. Try this one. Remember that launch is with atmospheric pressure.
[youtube]http://www.youtube/watch=qHbcsLp8dDI[/youtube]

Ping pong ball through a soda can.
[youtube]http://www.youtube/watch=zYqeRMbH798[/youtube]

saefroch · Fri Jun 17, 2011 9:11 pm

Erm... an atmosphere is a standardized unit. It just doesn't really have to indicate what the local atmospheric pressure is.

http://en.wikipedia.org/wiki/Atmosphere_(unit)