Part A The food calorie, equal to 4186 J, is a measure of how much energy is rel

Question

Part A 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 If a 61.0 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? Submit My Answers Give Up Part B If, as is typical, only 25.0 % 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.)

Explanation / Answer

Part A:

As we know that, gravitational PE = mass x gravity x height

The energy would be 4186 x 160 = 670000 J

Now suppose the hiker climbs to a height of h meter.

So,

670000 = 61 * 9.8 * h

=> h = 670000 / (61*9.8) = 1120.8 m.

Part B:

In this case, h = 1120.8 * (25 / 100) = 280.2 m

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