An engineer places a small sample of a material on a horizontal disk whose surface is made of another material and then rotates the disk from rest with a constant angular acceleration of 4 rad/s2. Assuming that the coefficient of static friction between the sample and disk is 0.2, what is the angular velocity of the disk at the time instant when the sample starts slipping on the disk

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?