An exhibit in a science museum requires the observer to use a pump to create air bubbles in a column of liquid. The bubbles then rise through the liquid.
(i) Complete the free-body force diagram for a bubble as it rises through the liquid.
(3)
*(ii) It is observed that larger bubbles reach the top of the column of liquid in less time than smaller
bubbles.
By considering the forces acting on a bubble as it rises, explain this observation.
(3)

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?