A small sculpture made of brass (density = 8470 kg/m cubed) is believed to have a secret central cavity. The weight of the sculpture in air is 15.76N. When it is submerged in water, the weight is 13.86 N. What is the volume of the secret cavity?
What's in the secret cavity? Air, hydrogen, nothing, or maybe the other extreme, something just a bit lighter than water, like gasoline? This has to be known in order to answer the question.