Absence of buoyant force when a fluid and submerged object are in free fall together can be demonstrated in two ways. In the first kind of demonstration, a submerged object whose density is lower than that of water doesn't go up in free fall because the buoyant force is absent. It has been demonstrated using a cork,1 Cartesian diver,2 and an air bubble.3
In the second kind of demonstration, a force that still acts in free fall can bring down an object less dense than water when the buoyant force is switched off in free fall. This has been demonstrated using an inflated balloon attached with a spring to the cap of an inverted water-filled bottle].4
We present a new demonstration of the second kind. The items needed for the demonstration are a round magnetic tray, a ring magnet (taken out of another magnetic tray), a...
