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[–] 129 points 9 hours ago (2 children)

A group of researchers was studying how different people solve problems. They gathered a physicist, a mathematician, and an engineer and gave them each a problem: find the volume of a red sphere. The mathematician solves it first. Asked how, he explains that he used a simple formula. The physicist solves it next. Asked how, he explains that he submerged the sphere in water and measured the rise in water level. Hours later, they find the engineer buried in paperwork. Asked about his progress, he says “I can only find a table of values for the volume of blue spheres.”

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  • [–] 86 points 8 hours ago* (2 children)

    On further inspection, it was found that the mathematician had assumed an ideal sphere of constant radius, while the real object was in fact oblate. The mathematician had neglected to take any measurements, leading to an incorrect value. The physicist's answer was correct, but only at sea level at nominal temperature.

    The engineer is currently using calipers to measure the diameter of the object at many different angles in order to build a CAD model. He said we could expect results next year.

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  • [–] 38 points 8 hours ago (3 children)

    The physicist’s answer would be correct anywhere, no matter the temperature or density of the fluid.

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  • [–] 8 points 7 hours ago* (2 children)

    Assuming the time between submersion and observation is greater than zero, increasing temperatures above boiling would give increasing error.

    Conversely the physicist may get other error at/near freezing.

    And yet another option is the fluid being above the Ball's melting and/or boiling point, assuming changes in density with phase change.

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  • [–] 6 points 7 hours ago (1 child)

    All of which the physicist can trivially account for, control and variable test around, should the requested question be updated to require it.

    The requested question did not include "In all possible scenarios", thus determining the volume of the sphere via physics calculation at the most average of conditions, is the most correct valid solution, absent further requirement parameters.

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  • [–] 2 points 6 hours ago*

    You're right in terms of grading a student's homework or whatever.

    In research/publication/career these assumptions must be stated unless given.

    But I was responding to:

    The physicist’s answer would be correct anywhere, no matter the temperature or density of the fluid.

    Which includes non-standard conditions.

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  • [–] 8 points 7 hours ago*

    Interestingly, the physicist's answer would always be correct, but not always consistent.

    If the sphere is compressible, then air pressure will slightly affect its volume. And unless the thermal expansion rate of the sphere is zero, the amount of fluid displaced will also vary with temperature.

    However, even if the physicist gets different answers in different environments, it's always still a correct answer, because they correctly measured the volume of the sphere at that time.

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