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# Energy is conventionally measured in Calories as well as in joules.One Calorie in nutrition is 1 kilocalorie, which we define inChapter 11 as 1 kcal = 4,186 J. Metabolizing 1 gram of fat canrelease 9.00 kcal. A student decides to try to lose weight byexercising. She plans to run up and down the stairs in a footballstadium as fast as she can and as many times as necessary. Is thisin itself a practical way to lose weight? yes no To evaluate the program, suppose she runs up a flight of90 steps, each 0.150 m high, in67.0 s. For simplicity, ignore theenergy she uses in coming down (which is small). Assume that atypical efficiency for human muscles is 20.0%. This means that whenyour body converts 100 J from metabolizing fat, 20 J goes intodoing mechanical work (here, climbing stairs). The rem # Energy is conventionally measured in Calories as well as in joules.One Calorie in nutrition is 1 kilocalorie, which we define inChapter 11 as 1 kcal = 4,186 J. Metabolizing 1 gram of fat canrelease 9.00 kcal. A student decides to try to lose weight byexercising. She plans to run up and down the stairs in a footballstadium as fast as she can and as many times as necessary. Is thisin itself a practical way to lose weight? yes no To evaluate the program, suppose she runs up a flight of90 steps, each 0.150 m high, in67.0 s. For simplicity, ignore theenergy she uses in coming down (which is small). Assume that atypical efficiency for human muscles is 20.0%. This means that whenyour body converts 100 J from metabolizing fat, 20 J goes intodoing mechanical work (here, climbing stairs). The rem

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Energy is conventionally measured in Calories as well as in joules.One Calorie in nutrition is 1 kilocalorie, which we define inChapter 11 as 1 kcal = 4,186 J. Metabolizing 1 gram of fat canrelease 9.00 kcal. A student decides to try to lose weight byexercising. She plans to run up and down the stairs in a footballstadium as fast as she can and as many times as necessary. Is thisin itself a practical way to lose weight?
yes
no
To evaluate the program, suppose she runs up a flight of90 steps, each 0.150 m high, in67.0 s. For simplicity, ignore theenergy she uses in coming down (which is small). Assume that atypical efficiency for human muscles is 20.0%. This means that whenyour body converts 100 J from metabolizing fat, 20 J goes intodoing mechanical work (here, climbing stairs). The remainder goesinto internal energy. Assume the student's mass is 57.0 kg.
(a) How many times must she run the flight ofstairs to lose 1 pound of fat?
(b) What is her average power output, in watts and in horsepower,as she is running up the stairs?
W
hp

## Answers (1) 2021-03-07
a) the amount of energy released by burning 1 lb offat is 1 lb (453.8 g / 1lb)(9 K cal / 1g)(4186J/1Kcal)= 1.71\times 107J mechanical energy out put is 1.71\times 107J (0.20) = n mg (no .of steps)height cos 0o 1.71\times 107J (0.20) = n (57.0 kg)(9.8 mis2)(90) (0.150 m )number of times she must climb the steps is n = [1.71\times 107J (0.20)] /(57.0 kg)( 9.8 mis2)(90 )(0.150m) simplify the above youwill get the answer
b) power output P = W/t = [ (57.0 kg)( 9.8 mis2)(90 )(0.150m)]/ 67.0 s simplify for the answer 1 h p = 746 W

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