# Homework Help: Water in a glass pipe

1. Jun 27, 2006

### Montana

Water in a glass pipe (pressure and volume)

Hi,
I have the following problem:we have a 1 meter long, thin glass pipe. It is open on both sides, we put that pipe 0,5 meters into a container filled with water. After that, we close the upper end which stucks out of the water, now we turn that pipe 180° around a horizontal axis, the air pressure is 105 kPa. Now I have to ascertain the height of the air column in the pipe.

I have the following ideas: first when we put the pipe into the water we have to add to the 0,5 meter the capillary force, I have an equation for that, but unfortunately I need the radius to calculate that. I guess I have to eliminate it somehow.
Now I have that water and when I turn the pipe arround I have to add the pressure of the water in the pipe (which is density of water*heigt*g) and the air pressure.
My suspicion is that the air in the pipe is pressed together a little bit because of that pressure. And that's all to it I imagine. But I have problems during calculation, because I can't get the radius out of my equations.

So I hope that anybody can help me, but PLEASE don't calculate anything in your answer (as far as possible) just give me a hint, because I want to solve it by myself (maybe later on I ask you to calculate something, but only if I'm completely exhausted Wink )
thanks

Last edited: Jun 27, 2006
2. Jun 29, 2006

### Montana

Does really nobody has an idea ?