A thing, rigid, spherical shell with a mass of 4.00 kg and diameter of 0.200 m is filled with helium at 0 degrees celsius and 1 atm pressure. It is then released from rest on the bottom of a pool of water that is 4.00 m deep.
A) determine the upward acceleration of the shell.
B) How long will it take for the top of the shell to reach the surface? disregard the frictional effects.