Concept explainers
The light energy that falls on a square meter of ground over the course of a typical sunny day is about 20 MJ. The average rate of electric energy consumption in one house is 1.0 kW.
a. on average, how much energy does one house use during each 24 h day?
b. If light energy to electric energy conversion using solar cells is 15% efficient, how many square miles of land must be covered with solar cells to supply the electric energy for 250,000 houses? Assume there is no cloud cover.
Want to see the full answer?
Check out a sample textbook solutionChapter 11 Solutions
College Physics: A Strategic Approach Plus Mastering Physics with Pearson eText -- Access Card Package (4th Edition) (What's New in Astronomy & Physics)
Additional Science Textbook Solutions
Campbell Biology (11th Edition)
Campbell Essential Biology with Physiology (5th Edition)
Biology: Life on Earth (11th Edition)
Campbell Biology: Concepts & Connections (9th Edition)
Campbell Essential Biology (7th Edition)
Human Biology: Concepts and Current Issues (8th Edition)
- (a) What is the average power consumption in watts of an appliance that uses 5.00 kW h of energy per day? (b) How many joules of energy does this appliance consume in a year?arrow_forward(a) How long will the energy in a 1470kJ (350kcal) cup of yogurt last in a woman doing work at the rate of 150 W with an efficiency of 20.0% (such as in leisurely climbing stairs)? (b) Does the time found in part (a) imply that it is easy to consume more food energy than you can reasonably expect to work off with exercise?arrow_forwardA 4ton air conditioner removes 5.60107J (48,000 British thermal units) from a cold environment in 1.00 h. (a) What energy input in joules is necessary to do this if the air conditioner has an energy efficiency rating (EER) of 12.0? (b) What is the cost of doing this if the work costs 10.0 cents per 3.60106J (one kilowatt—hour)? (c) Discuss whether this cost seems realistic. Note that the energy efficiency rating (EER) of an air conditioner or refrigerator is defined to be the number of British thermal units of heat transfer from a cold environment per hour divided by the watts of power input.arrow_forward
- (a) How long can you play tennis on the 800 kJ (about 200 kcal) of energy in a candy bar? (b) Does this seem like a long time? Discuss why exercise is necessary but may not be sufficient to cause a person to lose weight.arrow_forward(a) What is the average metabolic rate in watts of a man who metabolizes 10,500 kJ of feed energy in one day? (b) What is the maximum amount of work in joules he can do without breaking down fat, assuming a maximum eficiency of 20.0%? (c) Compare his work output with the daily output of a 187W (0.250horsepower) motor.arrow_forward(a) What is the average power consumption in watts of an appliance that uses 5.00kWh of energy per day? (b) How many joules of energy does this appliance consume in a year?arrow_forward
- The winning time for the 2005 annual race up 86 floors of the Empire State Building was 10 min and 49 s. The winner’s mass was 60 kg.a. If each floor was 3.7 m high, what was the winner’s change in gravitational potential energy?b. If the efficiency in climbing stairs is 25%, what total energy did the winner expend during the race?c. How many food Calories did the winner “burn” in the race?d. Of those Calories, how many were converted to thermal energy?e. What was the winner’s metabolic power in watts during the race up the stairs?arrow_forwardThe energy efficiency of electric vehicles is usually rated in terms of the kilowatt-hours (of energy) required to drive 100 miles, or kWh/100 mi. An electric car is rated at 38 kWh/100 mi. a. Is a vehicle rated 27 kWh/100 mi more or less efficient than this electric car? b. How much energy (in kilowatt-hours) is required to drive this electric car 260miles? c. Assuming electricity costs $0.14/kWh, how much does it cost to drive this electric car 350 miles?arrow_forwardA certain region currently has wind farms capable of generating 2,400 megawatts (2.4 gigawatts) of power. A. Assuming wind farms typically generate 35% of their capacity, how much energy in kilowatt-hours, can the region's wind farms generate in one year? Given that the average household in the region uses about 10,000 kilowatt-hours of energy each year, how many houses can be powered by these wind farms? B. One of the great advantages of wind power is that it does not produce the carbon dioxide emissions that contribute to global warming. On average, the energy produced from fossil fuels generates 1.5 pounds of carbon dioxide for every kilowatt-hour of energy. Suppose the region did not have its wind farms and the energy was instead produced from fossil fuels. How much more carbon dioxide would be entering the atmosphere each year in pounds?arrow_forward
- 2.B.83 Question Help v Suppose you require 2500 food Calories per day. a. What is your average power, in watts? b. How much energy, in joules, do you require from food in a year? Counting all forms of energy (such as gasoline, electricity, and energy for heating), the average person consumes about 350 billion joules of energy each year. Compare this value to the energy needed from food alone. a. What is your average power, in watts? Approximately (Round to the nearest whole number as needed.) wattsarrow_forwardThe food calorie, equal to 4186 JJ, is a measure of how much energy is released when food is metabolized by the body. A certain brand of fruit-and-cereal bar contains 145 food calories per bar. A. If a 71.0 kgkg hiker eats one of these bars, 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? Express your answer in meters. H=____________m B. If, as is typical, only 25.0 %% of the food calories go into mechanical energy, what would be the answer to part A? (Note: In this and all other problems, we are assuming 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.) Express your answer in meters. H=______________marrow_forwardAn average person is recommended to take in 2000 calories per day (8,400,000J), because they will lose this much energy to heat and work in a typical day. A. If on Saturday you take in 10,000,000J of heat energy through food, lose 5,000,000J to heat and lose 1,450,000J to work, what is your change in energy? B. If on a typical weekday, you actually take in 5,000,000J of heat energy, and lose a total of 12,000,500J (includes both heat and work loss), what is your change in energy? C. From your work in (a) and (b), in which scenario will you store fat for future energy use, and in which scenario will you use fat for energy?arrow_forward
- College PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningCollege PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegeCollege PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
- University Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice UniversityGlencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-Hill