Question for the Physics-Minded

[beamjockey]

Recently I bought a new can of coffee.

I removed its plastic lid, and admired the shiny foil seal. On one side, ordinary atmospheric pressure. On the other, "vacuum." Its rim is attached to the circular rim of the can. The forces on it balance into a smooth convex form.


I began to wonder:

What shape is this?

Paraboloid? Section of a sphere?

I'm thinking it's a catenary of rotation. Am I right?

Comments

[stickmaker.livejournal.com]

This made me think of the corrector plate for a Schmidt-Cassegrain telescope. The first one of those was made by sealing a sheet of optical glass across the mouth of an old kettle, pulling a vacuum inside, polishing the glass flat, and releasing the vacuum.