Question
A slightly deranged Arctic inventor surrounded by ice thinks it would be much less mechanically complex to cool a car engine by melting ice on it than by having a water-cooled system with a radiator, water pump, antifreeze, and so on.
1. If 80.0% of the energy in 1.00 gal of gasoline is converted into “waste heat” in a car engine, how many kilograms of $0^\circ\textrm{C}$ ice could it melt?
2. Is this a reasonable amount of ice to carry around to cool the engine for 1.00 gal of gasoline consumption?
3. What premises or assumptions are unreasonable?
1. $21 \textrm{ kg}$
2. Yes, it's possible to carry this much ice, but many journeys are long enough to consume much more than 1 gallon of gasoline. Average fuel efficiency in the United States of America is 25 mpg, and it's common to travel further than 25 miles. For long journeys carrying ice will become impractical.
3. Not all heat energy released by combustion goes into the engine. Much of it escapes through the exhaust. The practicality of obtaining so much ice is another problem with this cooling approach.

# OpenStax College Physics for AP® Courses, Chapter 14, Problem 77 (Problems & Exercises)

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