Speaker 1: Welcome to Brainstuff from house stuff Works dot com where
Speaker 1: smart happens. I am Marshall Brain with today's question, is
Speaker 1: there a way to compare a human being to an
Speaker 1: engine in terms of efficiency? It turns out that biological engines,
Speaker 1: which is what the muscles in your body are, are
Speaker 1: pretty amazing in terms of efficiency. To find out how efficient,
Speaker 1: let's look at how many calories a person burns while
Speaker 1: riding a bicycle. If you look on the web, you'll
Speaker 1: find that a person riding a bicycle at fifteen miles
Speaker 1: per hour or twenty four kilometers per hour burns about
Speaker 1: point o four nine calories per pound per minute. So
Speaker 1: a hundred and seventy five pound person burns five fifteen
Speaker 1: calories in an hour, or about thirty four calories per mile.
Speaker 1: That works out to twenty one calories per kilometer. A
Speaker 1: gallon of gasoline about four eaters, contains about thirty one
Speaker 1: thousand calories. If a person could drink gasoline, then a
Speaker 1: person could ride about nine hundred and twelve miles on
Speaker 1: a gallon of gas, or about three hundred sixty per leader.
Speaker 1: Considering that a normal car gets about thirty miles to
Speaker 1: a gallon that's pretty impressive. A human being on a
Speaker 1: bicycle is about thirty times more efficient than a car
Speaker 1: going down the road. To be fair, to keep in
Speaker 1: mind that a car generally weighs a ton or more,
Speaker 1: while a bicycle weighs only thirty pounds. Cars also travel
Speaker 1: a lot faster than fifteen miles per hour, but it's
Speaker 1: still an interest in comparison. Note also that people can't
Speaker 1: drink gasoline. However, people can drink vegetable oil, which contains
Speaker 1: nearly the same number of calories per gallon. The people
Speaker 1: riding in a race like the Tour de France are
Speaker 1: riding more like twenty five miles per hour. Because air
Speaker 1: resistance rises very quickly with speed, they're burning about three
Speaker 1: times more calories, something like a hundred calories per mile
Speaker 1: in a hundred miles stage of the tour. A racer
Speaker 1: might burn something like eight thousand to ten thousand calories
Speaker 1: in one day, so they're getting only about three hundred
Speaker 1: miles per gallon. The only way to replace those calories
Speaker 1: is to eat a lot of food. For more on
Speaker 1: this and thousands of other topics, is that how stuff
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