Calculate Weight

[Krishna prasad]

Hi,

I am a bit new to this area of physics.

My question:

1) How much minimum weight (in milligrams or grams) is required to keep 1 m3 (1 meter cube) of Helium / Hydrogen contained in a container of negligible weight at normal atmospheric pressure (outside pressure).

This question has been bugging me since my childhood and I am not able to gather an answer for this so long.

You could also mail me at prasad@pspindia.com which I would appreciate.

Thanks

Prasad

[JohnDubYa]

This is a common problem in most physics textbooks.

Essentially, you vector sum the forces acting on the container to 0, since the container is not accelerating (please, no general relativity). There are two forces acting on the container: the force of gravity F_g = mg and the buoyancy force F_B = \rho V g. Since they must vector cancel, set the two forces equal and solve for the mass m.