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 160 food calories per bar. 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? Part B If, as is typical, only 20.0 % of the food calories go into mechanical energy, what would be the answer to part (a)?

Explanation / Answer

(a) W = mgh
160 x 4186 = 70 x 9.8 x h

height h=976.32 m

(b) Only 20% of food energy isavailable.

Then, E x 0.20 = mgh'

          Height, h' = 160x4186x0.20/(70x9.8)

                         = 195.26 m

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