2 ms·
I think of the example of holding a beachball under water. The farther under the water you hold it, the more explosively it will leap out of control when you do
by patrickg_zill 8y ago
I think of the example of holding a beachball under water. The farther under the water you hold it, the more explosively it will leap out of control when you do let it go.
- burfog 8y agoThe example is broken. Air is much more compressible than water. Pressure will be almost a linear function of depth because water isn't very compressible. From the depth at which pressure is equalized inside and outside the beachball, until reaching the depth at which the ideal gas law becomes inaccurate, the volume of the beach ball will be simple function of depth. Doubling the depth will halve the volume. Beyond that, the volume will collapse faster, until the air becomes a supercritical fluid with density similar to that of the water. In any case, the ball shrinks as you go deeper. Buoyancy is roughly the density of the water times the volume of the ball. (the air inside is of trivial mass) The water density doesn't change much because water is not very compressible, but the volume of the ball decreases. This reduces the buoyancy force. Suppose the ball is made of PVC, which sinks in water. Once the air has been pretty well compressed, the average density of the ball (air and PVC) will exceed that of water. The ball thus sinks.