1. An airplane takes off from a coastal city where the air temperature is 20 °C (68 °F) and climbs to cruising altitude. At what altitude will the outside temperature be 0 °C?
(Assume that there is no temperature inversion like those which occur in the Los Angeles area.)
2. Consider a cyclic equilibrium process made up of following sub processes:
a → b is isothermal with increasing volume;
b → c is at constant volume with decreasing pressure;
c → a is adiabatic.
(a) Sketch the process on a PV diagram.
(b) Complete the following table with numerical values. (Use a separate piece of paper.) Justify your answers, and use the numbers in the table to identify your justifications.
|
Sub process
|
Q
|
ΔU
|
W
|
|
a → b
|
3600 J
|
(3)
|
(7)
|
|
b → c
|
(1)
|
(4)
|
(8)
|
|
c → a
|
0
|
(5)
|
-1200 J
|
|
Complete cycle
|
(2)
|
(6)
|
(9)
|
(c) Find the energy efficiency of the process.