A food calorie is equal to 1 kcal or 4186 J. An average person burns about 4000

Question

A food calorie is equal to 1 kcal or 4186 J. An average person burns about 4000 kcal per day.

(a) What is the average rate of energy expenditure of a person who requires 4000 kcal in a day (Where does all that energy go?)

(b) A person weighing 160 kg hikes up Mt. Si, gaining an elevation of about 1000m. How many kcal of energy are needed to reach the top? (You can assume the conversion of internal energy to work has an efficiency of only 20%).

(c) How much energy is required by the person to hike down from Mt. Si?

** if you're not sure about your solution or ansawer, please don't respond, Thanks**

Explanation / Answer

a) 4000 kcal/day = 4000*4186 joules/24*60*60 joules/sec =193.796 joules/second

b) energy required = mgh = 160*1000*9.8 = 1568000 joules

internal energy needed = 1568000/0.2 *4186 kcal = 1872.9096 kcal

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