1. what do the letters P. P.E stand for in construction,?
2. what were the three types of P. P.E for our ¨eyes¨ ?
3. name two types of P. P.E for our ears (remember ear buds are not one of them)

Air inially occupying a volume of 1 m2 at 100 kpa, 27 c undergoes three internally reversible processes in series. process 1-2 compression to 500 kpa during which pv constant process 2-3 adiabatic expanslon to 100 kpa process 3-1: constant-pressure expansion to 100 kpa (a) calculate the change of entropy for each of the three processes. (b) calculate the heat and work involved in each process. (c) is this cycle a power cycle or refrigeration cycle?