An elastic string of natural length 0.8 m and stiffness 70 nm-1 has one end attached to the ceiling and a mass of 2 kg attached at the other end. the mass is pulled down so that the string extends by 0.60 m and then released. assuming that energy is conserved find the velocity of the mass when the string returns to its natural length.

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?