Physics 201 MWF10:20 Fall 1995 (Ford)
Exam IV Chapts. 14--19 in SZY College Physics
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(18 pts) 1. Mass m of ice at an initial temperature of -40 °C is
placed in 3.00 kg of water that is in a container of negligible mass. The
3.00 kg of water has an initial temperature of 20.0 °C. The final
temperature of the system is 12.0 °C. No heat is lost to the
surroundings. What is the mass m of the ice?
(Note: For water
c = 4190 J/kg·C°,
LF = 333×103 J/kg,
LV = 2256×103 J/kg,
For ice c = 2010 J/kg·C°.)
Ans. __________________
(14 pts) 2. A glass flask with a narrow stem is completely filled with
800 cm3 of liquid, with both the liquid and the flask at a
temperature of 25.0 °C. When the liquid and flask are heated to a
temperature of 75.0 °C, 3.2 cm3 of liquid overflows from
the flask. The coefficient of volume expansion of the liquid is
9.00×10-5/C°. What is the coefficient of volume
expansion of the glass?
Ans. __________________
(16 pts) 3. One end of an insulated rod is maintained at a temperature of
400 °C. The other end is in water at
T = 100 °C and p = 1 atm.
The rod has length 0.300 m and cross section area
A = 5.00×10-4 m2.
The heat conducted by the rod converts 0.0042 kg of liquid water at
100 °C into steam at 100 °C in 5.00 minutes. (See problem 1 for
useful data for water.)
a) What is the heat current H in the rod?
Ans. ________________
b) What is the thermal conductivity of the rod? (You must express
your answer in units of J/s·m·C°.)
Ans. ________________
(18 pts) 4. A cylinder contains 2.0 moles of an ideal gas at an initial
temperature of 350 K and an initial pressure of 1.5×105 Pa.
With
the pressure of the gas kept constant the gas is compressed until its volume
is halved (V2 = V1/2). For this gas the
molar heat capacity at constant
volume is Cv = 12.47 J/mol·K.
a) What is the work W for this process? (Your answer must
specify whether W is positive or negative.)
Ans. ___________________
b) What is the change in internal energy of the gas this process? (Your
answer must
specify whether 
U is positive or negative.)
Ans. __________________
(18 pts) 5. A Carnot heat engine has a thermal efficiency of 60%. The
low-temperature reservoir has a temperature of 200 K and the engine exhausts
300 J of heat into the low-temperature reservoir each cycle. Calculate
a) the temperature of the high-temperature reservoir.
Ans. __________________
b) the amount of heat that in each cycle flows from the high-temperature
reservoir into the engine.
Ans. _________________
c) the work W done by the engine during each cycle.
Ans. ________________
(16 pts) 6. A system is taken around the cycle shown in the sketch.
Process 2 to 3 is adiabatic, 3 to 1 is at constant pressure,
and process 1 to 2 is at constant volume. For process
1 to 2 the heat flow is Q = +720 J and for process 3 to 1
the heat flow is Q = -530 J. For process 2 to 3 the work is
W = 270 J.
What is the work W for process 3 to 1? (Your answer must
specify whether W is positive or negative.)
Ans. _______________