Unformatted text preview: PHY 3062 Thermal Physics: Midterm Examination 1
Professor Mark W. Meisel, Department of Physics, University of Florida
20 September 2001 1. Brief, tothepoint responses please. A. (4 points) on a P versus T graph, sketch a typical phase diagram for a material that
contracts on freezing. You need to label all phases, all lines, and all important points. B. (5 points) For a reversible, isothermal process involving an ideal gas, how much work
is needed to move the system from V1 to V2? C. (4 points) Consider the following expression and state if it is an exact differential.
Justify your answer. The expression is rdx = (3y2 + 4yz)dy + (2yz + y2)dz V D. (2 points) Is it possible to have the solid, liquid, and gas phases of a substance coexisting
in equilibrium? If no, why not. If yes, give an example. 2. (7 points) A glass bottle of nominal capacity 250 cm3 is ﬁlled brim full of water at 20°C. If the
bottle and contents are heated to 50°C, how much water spills over? (For water under these
conditions, cP = 4200 J kg‘1 K‘1 and ,6 = 0.21 x 10‘3 K4. Assume that the expansion of
the glass is neglibible.) 3. During the ascent of a meteorological balloon, its volume increases from 1 m3 to 1.8 m3, and
the pressure of the ideal gas inside the balloon decreases from 1 bar to 0.5 bar. The internal
energy of the gas is U = aT, where or is 800 UK. A. (4 points) Assume that in this process (the ascent) V = AP + B. Find A and B.
B. (4 points) If the initial temperature is 300 K, what is the ﬁnal temperature? C. (6 points) How much work is done by the gas in the balloon? D. (4 points) How much heat does it absorb? V4. (10 points) A long U—tube, as shown in the ﬁgure, has uniform cross section A and contains
a ﬂuid with density p to the depth shown. This ﬂuid rises to a height h as shown in the ﬁgure,
where x/Z < h. The barometn'c pressure is P0. The left side of the tube is now closed at the
top, and the right side is connected to a good vacuum pump. The ﬂuid level drops a distance 13 on the left side while rising by the same distance on the right side. Derive the quadratic
equation that is necessary to solve for Z in terms of h, Po, p, and g which is the acceleration due to gravity. / A x A 1
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