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Re: Fish tank in orbit?



Leigh Palmer wrote:

If the fish were to *coast* into the bubble, however, it
would (by conservation of momentum) come to rest just as it
reached a position fully inside the air space! The problem is
even more interesting in this case.


Can you elaborate on why conservation of momentum would cause the
fish to come to rest inside the air bubble. I don't see it
necessarily stopping inside the bubble.

You're scepticism is well founded; it would appear I reacted too
hastily.

What is the translational momentum of a tank of water containing a
fish having the density of water and moving with a velocity <v> if
the boundary of the tank is at rest in an inertial system? I get
zero. Emergence of the coasting fish into the air in the bubble is
a collision of a sort between the fish and the remainder of the
system. If the collision is not perfectly inelastic the fish will
drift across the bubble; she will not be discombubblated. The
perfectly inelastic solution is the one I lept to too quickly.

Somehow this reminds me of Feynman's sprinkler problem.

Leigh