BIO Doughnuts: Breakfast of Champions! Atypical doughnut contains 2.0 g of protein, 17.0 g of carbohydrates, and 7.0 g of fat. Average food energy values are 4.0 kcal/g for protein and carbohydrates and 9.0 kcal/g for fat. (a) During heavy exercise, an average person uses energy at a rate of 510 kcal/h. How long would you have to exercise to “work off” one doughnut? (b) If the energy in the doughnut could somehow be converted into the kinetic energy of your body as a whole, how fast could you move after eating the doughnut? Take your mass to be 60 kg, and express your answer in m/s and in km/h.
BIO Doughnuts: Breakfast of Champions! Atypical doughnut contains 2.0 g of protein, 17.0 g of carbohydrates, and 7.0 g of fat. Average food energy values are 4.0 kcal/g for protein and carbohydrates and 9.0 kcal/g for fat. (a) During heavy exercise, an average person uses energy at a rate of 510 kcal/h. How long would you have to exercise to “work off” one doughnut? (b) If the energy in the doughnut could somehow be converted into the kinetic energy of your body as a whole, how fast could you move after eating the doughnut? Take your mass to be 60 kg, and express your answer in m/s and in km/h.
BIO Doughnuts: Breakfast of Champions! Atypical doughnut contains 2.0 g of protein, 17.0 g of carbohydrates, and 7.0 g of fat. Average food energy values are 4.0 kcal/g for protein and carbohydrates and 9.0 kcal/g for fat. (a) During heavy exercise, an average person uses energy at a rate of 510 kcal/h. How long would you have to exercise to “work off” one doughnut? (b) If the energy in the doughnut could somehow be converted into the kinetic energy of your body as a whole, how fast could you move after eating the doughnut? Take your mass to be 60 kg, and express your answer in m/s and in km/h.
A food calorie is a unit of energy such that 1 food calorie = 4184 J. This means that a person that burns energy with a power of 4184 W would burn one food calorie every second. A more typical human power rate is 90 W (called the basal metabolic rate). At this rate, how many calories are burned per second (or alternatively, how many seconds does it take to burn 1 calorie)?
The food calorie, equal to 4186 J, is a measure of how much energy is released when food is metabolized by the body. A Milo Bar contains 180 food calories per bar. (a) If a 70-kg hiker eats one Milo Bar, how high a mountain must he climb to “work off” the calories, assuming that all the food energy goes only into increasing gravitational potential energy? (b) If, as is typical, only 20% of the food calories go into mechanical energy, what would be the answer to part (a)? (NOTE: In this problem, we assume that 100% of the food calories that are eaten are absorbed and used by the body. This is actually not true. A person’s “metabolic efficiency” is the percentage of calories eaten that are actually used; the rest are eliminated by the body. Metabolic efficiency varies considerably from person to person.)
The total consumption of electrical energy in the United States is about 1.0 1019 joules per year. What is the average rate of electrical energy consumption in watts? If the population of the United States is 300 million, what is the average rate of electrical energy consumption per person? The sun transfers energy to the earth by radiation at a rate of approximately 1.0 kW per square meter of surface. If this energy could be collected and converted to electrical energy with 40 % efficiency, how great an area (in square kilometers) would be required to collect the electrical energy used by the United States?
Chapter 17 Solutions
University Physics with Modern Physics, Volume 2 (Chs. 21-37); Mastering Physics with Pearson eText -- ValuePack Access Card (14th Edition)
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