Question

help with part C and D

Answer 1

Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is one kilocalorie, defined as 1 kcal = 4186 J. Metabolizing 1 gram of fat can release 9.00 kcal. A student decides to try to lose weight by exercising. She plans to run up and down the stairs in a football stadium as fast as she can and as many times as necessary. To evaluate the program, suppose she runs up a flight of 85 steps, each 0.15 m high in 75.0 s. For simplicity, ignore the energy she uses in coming down (which is small). Assume that a typical efficiency for human muscles is 20.0 %. This statement means that when your body converts 100 J from metabolizing fat, 20 J goes into doing mechanical work (here, climbing stairs). The remainder goes into extra internal energy. Assume the student's mass is 65 kg.
(a) What is work she has done to run up a flight of 85 steps?
(b) What is her average power output, in watts, as she is running up the stairs?
(c) How many times must she run the flight of stairs to lose 1 kg of fat?
(d) Is this activity in itself a practical way to lose weight?