What is the gravity force between a gas bubble and a mass of iron in a bottle of water floating in space?(distant form any other source of gravity)

Question

I'd like to study the gravitational interaction between a bubble of gas and a positive mass in a fluid. The mass should have a density greater the the fluid density, the bubble instead lower.

I'd like the analysis to be conducted in 2 different ways:

1. without the concept of negative mass using only Newton Law and Buoyancy.
2. with the concept of negative mass.

(the results should be of course the same)

Answer 1

There is a mutual repulsive force between the bubble (which is lighter than the water) and the iron mass (which is heavier than the water). They will tend to move away from each other. The forces are due primarily to the pressure gradient induced by the gravitational fields from the iron mass and the bubble (absence of water mass).

See the analysis here