APK3110_Ch6_Work_Spring12

APK3110_Ch6_Work_Spring12 - MEASUREMENT OF WORK, POWER, AND...

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MEASUREMENT OF WORK, POWER, AND ENERGY EXPENDITURE Chapter 6 1 of 29
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Objectives 1. Define the terms work , power , energy , and net efficiency . 2. Give a brief explanation of the procedure used to calculate work performed during: (a) cycle ergometer exercise and (b) treadmill exercise. 2 of 29 Chapter 6
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Units of measure English system used in United States Metric system standard system of measurement in science advantage because subdivisions or multiples of its units are 10 System International (SI) units For standardizing units of measurement in reporting of scientific data Allows easier comparison of published values Chapter 6 3 of 29
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Common metric system prefixes Chapter 6 4 of 29
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Important SI units Chapter 6 5 of 29
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Definition of work Work = force x distance In SI units: Work ( J ) = force ( N ) x distance ( m ) Example: Calculate the work performed in lifting a 100-kg weight up a distance of 1 m 100 kg * 9.79 N/kg = 979 N Work=979 N x 1 m = 979 N m = 979 J because 1 N m = 1 J Chapter 6 6 of 29
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Common units used to express work performed or energy expenditure Chapter 6 7 of 29
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Definition of power Power = work ÷ time Work rate or power output provides the intensity of exercise In SI units: Power ( W ) = work ( J ) ÷ time ( s ) Example: Performing 20,000 J of work in 60 s 20,000 J ÷ 60 s = 333.33 J•s –1 1 W = 1 J•s –1 , so 333.33 J•s –1 = 333.33 W Chapter 6 8 of 29
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Common units used to express power Chapter 6 9 of 29
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Subject steps up and down at specified rate Example: 70-kg subject, 0.5-m step, 30 steps•min –1 for 10 min Total work = force x distance Force = 70 kg x 9.79 N•kg –1 = 685.3 N Distance = 0.5 m•step –1 x 30 steps•min –1 x 10 min = 150 m Power = work ÷ time Measurement of work and power Ergometer: bench step 685 N x 150 m = 102,795 J (or 102.8 kJ) 102,795 J ÷ 600 s = 171.3 W Chapter 6 10 of 29
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Measurement of work and power Cycle Ergometer Stationary bicycle that allows accurate measurement of work performed Example: Duration of exercise=10 min Resistance against flywheel=1.5 kg (or 14.7 N) Distance traveled per pedal revolution=6 m
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This note was uploaded on 02/15/2012 for the course APK 3110C taught by Professor Dr.christou during the Spring '11 term at University of Florida.

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APK3110_Ch6_Work_Spring12 - MEASUREMENT OF WORK, POWER, AND...

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