The food calorie, equal to 4186 J, is a measure of how much energy is released when the body metabolizes food. A certain fruit-and-cereal bar contains 140 food calories. (a) If a 65 kg hiker eats one bar, how high a mountain must he climb to “work off” the calories, assuming that all the food energy goes into increasing gravitational potential energy? (b) If, as is typical, only 20% 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 not true. A person’s “metabolic efficiency” is the percentage of calories eaten that are actually used; the body eliminates the rest. Metabolic efficiency varies considerably from person to person.)
The food calorie, equal to 4186 J, is a
measure of how much energy is released when the body metabolizes
food. A certain fruit-and-cereal bar contains 140 food calories. (a) If
a 65 kg hiker eats one bar, how high a mountain must he climb to
“work off” the calories, assuming that all the food energy goes into
increasing gravitational potential energy? (b) If, as is typical, only
20% 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 not true. A person’s “
is the percentage of calories eaten that are actually used; the
body eliminates the rest. Metabolic efficiency varies considerably
from person to person.)
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