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

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 145 food calories per bar.



If a 74.0 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?
h =
837 m



Part B
If, as is typical, only 24.0 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.)

I have tried 138.5, but that is incorrect

Explanation / Answer

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 135 food calories per bar. 1 Food calorie must equal 1 Kilo calorie, because 1 calorie = 4.180 joules. A-) If a 70.0 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? Work = Energy Work = Force * distance When you climb, force = weight Weight = mass * gravity Work = mass * gravity * distance Work = 70 * 9.8* d Energy = 135 food calories * 4180 J/ food calorie =564,300 J Work = Energy 70 * 9.8* d = 564,300 d = 822.6 meters B-) If, as is typical, only 23.0% 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.) Energy = 0.23 * 564,300 = 129,789 Work = Energy 70 * 9.8* d = 129,789 d = 189.2 meters

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