Barometer

[binkaz]

i'm wondering what would happen to the barometer if it is in a spaceship in earth's orbit?

 

will the mercury float out since there is no gravity acting on it?

 

can i still measure the air pressure in the space ship?

 

will the air pressure in the ship hold the mercury in the baromater?

 

somebody pls tell me....

[Turtle]

___I don't know for sure about a mercury-tube-barometer; I think the liftoff might somehow empty it? Anyway, aneroid barometers have everyday use as altimeters & if you lauch into space with one in the capsule, it will read the pressure only in the capsule. If you vent it to outside, it will drop with altitude until it reaches its lowest physically-possible reading - pegged.

:P

http://www.bom.gov.au/info/aneroid/aneroid.shtml

[Tormod]

I thought most barometers used springs and not mercury. Do you mean a thermometer?

 

If you mean a thermometer, yes, I assume the mercury would flow out in microgravity. Pressurized in this context only means that sensors and valves make sure atmosphere stays at close to 1 bar (the same as sea level). There would be nothing keeping the mercury inside the container, unless it was sealed up.

[binkaz]

 

the barometer i'm talking about is sth like this..

 

lets say it is already in space, not taling into account the lift off part..

 

so is it still able to measure the air pressure in the space ship?

 

i was thinking, the mercury would be weightless in the ship as the ship is in orbit and is falling to earth..

[Tormod]

Yes, the mercury would be nearly weightless and would flow out.

[Boerseun]

No - won't work. The weight of the mercury is sucking on the vacuum. In orbit, the vacuum would just suck all the mercury up so the weight of the fluid column won't act as a pressure difference indicator.

[Turtle]

___Mmmmm....From your drawing, I tend to think the mercury stays in from the cabin pressure. This is intuitive on my part. ;) This means yes, it still works as a barometer. The better physicists here may offer a precise analysis to affirm or contradict my intuition. The issue perhaps is not the mercury's weight, but its mass? Perhaps the orientation of the barometer in relation to the spacecraft's direction of travel is an affecting influence as well? :P

[Qfwfq]

Boerseun is right Turtle, because that type of barometer relies on the weight of the mercury and hence on g being the usual value. It will give you readings slightly dependent on location on Earth too.

 

An aneroid barometer is better on a spaceship.