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tankster tankster
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5 years ago
A gas expands at constant temperature from an initial volume of 0.040 m3 and an initial pressure of 210 kPa until its pressure drops to 135 kPa. How much work is done by the system?
A) 3.0 kJ
B) 3.7 kJ
C) 4.1 kJ
D) 5.6 kJ
E) 7.9 kJ
Textbook 

Physics


Edition: 4th
Author:
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longhairlonghair
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5 years ago Edited: 10 months ago, bio_man
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B

For Ideal Gas and constant temperature expansion:

PV = ( P1 ) ( V1 ) = ( P2 ) ( V2 ) = Constant = K

( P1 ) ( V1 ) = ( 0.040m3 ) ( 210 kpa ) = 8.4 kPa.m3

K = 8.4 kPa.m3 = 8400 N - m. = 8400 J

Work done = Integral P dV = K / V dV ) = ( K ) [ Ln ( V2 / V1 ) ]

Work done  = ( K ) [ ln ( V2 / V1 ) ]

V2 = K / P2

V2 = 8.4 / 135 = 0.062 m3

Work done = ( 8400 ) [ ln ( 0.062 / 0.04000 ) ]

Work done = 3681 J = 3,681 kJ ~ 3.7 kJ

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2 months ago
Thx
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