结构推理 A particle is a hollow sphere of a metal oxide. The density of the metal oxide is 2000kg/m. The hollow portion in the center of the sphere is full of air that has the same density as the surrounding air through which the sphere is falling at its terminal velocity. The outside diameter of the sphere is 10and the thickness of its walls is 0.1(i.e., the bubble in the center has a diameter of 9.8).How fast is it falling?