[Phys-L] Re: Buoyancy question

[jsd at AV8N.COM (John Denker)]

Fakhruddin, Hasan wrote:
> I have a question pertaining to buoyancy phenomenon:
>
> What's the condition that a piece of iron released gently on the surface
> of water sink? Ignore surface tension.

Sorry, in general that involves a lot more than buoyancy.

In particular, consider an open cup.  If you design it
right, it will float:  it's an iron boat.

If you design it wrong, it might capsize and sink
immediately.

The stability of a boat is determined by rather
complicated considerations.  For starters, try
   http://www.google.com/search?q=boat+stability+metacenter
and see what you can find.

==============

If you meant to ask about a macroscopic everywhere-convex
solid piece of iron, it sinks unconditionally, as is well
known.