Along cylinder of diameter di slides at a velocity u inside a long stationary tube of diameter d2, so that the cylinder and tube are concentric. if the gap is filled with a fluid of viscosity ? , and if the fluid velocity varies linearly across the (small)gap, find the force per unit length required to keep the inner cylinder moving at a constant velocity.

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?