Suppose you spend 30.0 minutes on a stair-climbing machine, climbing at a rate of 75 steps per minute, with each step 8.00 inches high. If you weigh 150 lb and the machine reports that 700 kcal have been burned at the end of the workout, what efficiency is the machine using in obtaining this result? % If your actual efficiency is 0.17, how many kcal did you really burn? kcal

Suppose you spend 30.0 minutes on a stair-climbing machine, climbing at a rate of 75 steps per minute, with each step 8.00 inches high. If you weigh 150 lb and the machine reports that 700 kcal have been burned at the end of the workout, what efficiency is the machine using in obtaining this result? % If your actual efficiency is 0.17, how many kcal did you really burn? kcal

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter18: Heat Engines, Entropy, And The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 13P

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A 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.
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(a) How much food energy will a man metabolize in the process of doing 35.0 kJ of work with an efficiency of 5.00%? (b) How much heal transfer occurs to the environment to keep his temperature constant? Explicitly show how you follow the steps in the Problem—Solving Strategy for thermodynamics found in Problem-Solving Strategies for Thermodynamics.
(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?
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