MasterPhysics 4 soln

# MasterPhysics 4 soln - PHYS-408 Fall 2008 Mastering Physics...

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PHYS-408 Fall 2008 Mastering Physics Assignment #4 Solutions Problem 17.2 (a) How much work is done on the gas in the process shown in the figure? The work is just the negative of the area under the path. This can be done analytically, or you can just find the area. For a right triangle it is half the area of the corresponding square, so we can take 300 kPa to get the area under the path. (If this were a more complex shape, this would not work.) W = 300,000 Pa 300 cm 3 100 cm 3 ( ) 100 cm / m ( ) 3 = 60 J Problem 17.10 A gas is compressed from 600 cm 3 to 200 cm 3 at a constant pressure of 400 kPa. At the same time, 100 J of heat energy is transferred out of the gas. (a) What is the change in thermal energy of the gas during this process? The work done on the gas is just W = pdV = p Δ V = 400,000 Pa 200 cm 3 600 cm 3 ( ) 100 cm / m ( ) 3 = 160 J The change in thermal energy is just Δ E therm = W + Q = 160 J 100 J = 60 J Problem 17.16 (a) What is the maximum mass of lead you could melt with 1000 J of heat, starting from 20 degree(s) C? To change solid lead (symbol Pb) into liquid you must first heat it to its melting temperature, T mPb = 328 o C . Since we are starting at 20 o C , we get Δ T Pb = 328 o C 20 o C = 308 K (Here we take advantage of the fact that the change in temperature in Celsius and Kelvin

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MasterPhysics 4 soln - PHYS-408 Fall 2008 Mastering Physics...

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