Periodic time is the time taken for one complete oscillation by a body in circular motion. In this case the merry-go round takes 2 minutes to cover 15 complete oscillations. 2 Minutes = 120 seconds Hence, 15 oscillations takes 120 secs thus 1 oscillation takes 120/15 = 8 seconds therefore the period of the merry-go-round = 8 seconds
Because the temperature of the place its contained in is constantly changing, for example, if you put a room temperature item in the fridge it will become cold, or whatever the temperature you set your fridge to.
