The food calorie, equal to 4186 J , is a measure of how much energy is released

Question

The food calorie, equal to 4186 J , is a measure of how much energy is released when food is metabolized by the body. A certain brand of fruit-and-cereal bar contains 160 food calories per bar

A) If a 69.0 Kg hiker eats one of these bars, how high a mountain must he climb to "work off" the calories, assuming that all the food energy goes only into increasing gravitational potential energy?

B) If, as is typical, only 22.0 percent of the food calories go into mechanical energy, what would be the answer to part (a)? (Note: In this and all other problems, we are assuming that 100 % of the food calories that are eaten are absorbed and used by the body. This is actually not true. A person's "metabolic efficiency" is the percentage of calories eaten that are actually used; the rest are eliminated by the body. Metabolic efficiency varies considerably from person to person.)

Explanation / Answer

ANSWER 1. Gravitational PE = mass x gravity x height The energy would be 4186 x 160 = 670,000 J 670,000 = 65(9.8) h h = 1051 m 2. h = 1051(25%/100) = 263 m

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