Class Exercise 2 – Work & Energy Transfer
1. A piston cylinder device, containing 0.5 kg of gas undergoes a constant pressure
process at 4 bar, beginning at initial specific volume,
1
v0.8 m3/kg. The work done
during the process is –100 kJ. Determine the final volume of the gas, in m3.
[0.15 m3]
2. Air in a closed system changes states from state a to state b, as shown in FIGURE Q2.
When the change follows the path acb, 84 kJ of heat flows into the system and 32 kJ of
work is done by the system. Determine the heat transfer when the system changes
along:
a. Path adb, if 10.5 kJ of work is done by the system.
b. The curved path ba, if work done on the system is 21 kJ.
[62.5 kJ; -73 kJ]
FIGURE Q2
3. Heat is supplied to the system shown in FIGURE Q3,
a. explain what happened to pressure, temperature and volume of the system,
b. show the direction on energy transfer (+ve, -ve or zero).
FIGURE Q3
c b
a d
