A Cartesian diver toy consists of a small, partly water-filled dropper sealed inside a plastic bottle completely filled with water and then capped.
(a) Describe briefly how the Cartesian diver is constructed.
(b) When the sides of the bottle are squeezed, the diver sinks to the bottom; when the pressure on the bottle is released, it rises again. Explain these observations using the ideas of pressure, volume change of trapped air, and buoyant force.
(c) Initially the diver displaces 15cm3 of water and contains 4cm3 of trapped air at atmospheric pressure. Qualitatively explain how a reduction of the trapped air volume by about 0.5cm3 during squeezing changes the average density of the diver and causes its motion.