Energy is conventionally measured in Calories as well as in joules.One Calorie i

Question

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 g of fat can release 9.00 kcal. A studentdecides to try to lose weight by exercising. She plans to run upand down the stairs in a football stadium as fast as she can and asmany times as necessary. Is this in itself a practical way to loseweight? To evaluate the program, suppose she runs up a flight of100 steps, each 0.150 m high, in65.5 s. For simplicity, ignore theenergy she uses in coming down (which is small). Assume that atypical efficiency for human muscles is 20.0%. Therefore when yourbody converts 100 J from metabolizing fat, 20 J goes into doingmechanical work (here, climbing stairs). The remainder goes intoextra internal energy. Assume that the student's mass is51.0 kg.

(a) How many times must she run the flight of stairs to lose 1 lbof fat?
1 times

Explanation / Answer

one pound is   453.92 grams . So the energy released when this amount of fat is burnedis    453.92 * 9.00 = 4085.26 kcal= .         = 17100915Joules . Mechanical work running up steps = 51.0 * 9.80 * 100 * 0.15 =    7497Joules . Fat energy burned running stairs = 37485 Joules . Number of times to run stairs = 17100915 /37485 =    456 times

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.