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15. If a person has a dangerously high fever, submerging her in ice water is a bad idea, but an ice pack can help to quickly bring her body temperature down. How many grams of ice at 0C will be melted in bringing down a 60 kg patient's fever from 40C to 39C?

16. Legend has it that Archimedes was asked by King Hiero of Syracuse to determine whether a crown was pure gold or had been adulterated with a less valuable metal by an unscrupulous goldsmith. It was this problem that led Archimedes to the principle that bears his name. In a modern version of his method, a crown weighing 8.30 N is suspended underwater from a string. The tension in the string is measured to be 7.81 N. Is the crown pure gold?

17. A 2.0 g latex balloon is filled with helium. When it is completely inflated, its shape is approximately spherical with a diameter of 24 cm. If the balloon is released, what is its initial upward acceleration?