A 6 cm diameter rubber ball weighing 5 g is used to plug a 4 cm hole in the base of a tank. The tank is in use and is gradually emptying. At approximately what depth will the ball plug fail by floating up and out of the hole?

Rooms in the lower level of a cruise ship have 30 cm diameter circular windows known as portholes. In rough weather the lower portholes can be momentarily submerged up to 4 m by waves. Determine the instantaneous hydrostatic force in terms of magnitude and position at one of these moments.