A 59-kg woman cheats on her diet and eats a 457-Calorie (457 kcal) jelly doughnu

Question

A 59-kg woman cheats on her diet and eats a 457-Calorie (457 kcal) jelly doughnut for breakfast. (a) How many joules of energy are the equivalent of one jelly doughnut? =______ J (b) How many stairs must the woman climb to perform an amount of mechanical work equivalent to the food energy in one jelly doughnut? Assume the height of a single stair is 15 cm. =________ stairs (c) If the human body is only 27% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast? =________stairs

Explanation / Answer

a) 457x 1000x 4.184 =1912088 J b)work done = mgh= 1912088 h= 3306.96 m no. of stairs = 3306.96/0.15 = 22046 stairs c) h = 1912088* 0.27 /(59*9.8) = 892 m no. of stairs =892/0.15 = 5952 stairs

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