I won't answer the main part of this question as I know what the added massOriginally Posted by bobbyk
for a sphere is under these conditions. But I will discuss the expectation that
the acceleration would be -g.
The simple minded analysis would be: In the absence of added mass the
force acting on sphere is -mg, where m is the mass of displaced air,
and there is a minus sign because g is downwards acting and the
buoyancy force is upwards. The mass being accelerated is near zero, so
the acceleration should be very large, and not -g. (identically zero
mass as required by the thought experiment would give infinite acceleration).
RonLThe problem was reportedly given to Feynman, and, after working on it for a
number of hours, came up with the answer. I won't tell you now what he got, but will leave it for those who might want to try to solve it. I don't know how Feynman did it, but will post his answer later on.