How much work is done by the motor in a cd player to make a cd spin, starting from rest? the cd has a diameter of 12.0 cm and a mass of 15.8 g. the laser scans at a constant tangential velocity of 1.20 m/s. assume that the music is first detected at a radius of 27.0 mm from the center of the disk. ignore the small circular hole at the cd’s center.

4r-134a enters the condenser of a residential heat pump at 800 kpa and 50°c at a rate of 0.022 kg/s and leaves at 750 kpa subcooled by 3°c. the refrigerant enters the compressor at 200 kpa superheated by 4°c determine (a) the isentropic efficiency of the compressor, (b) the rate of heat supplied to the heated room, and (c) the cop of the heat pump. also, determine (d) the cop and rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kpa. (0.757, 4.37 kw, 5.12, 6.18, 3.91 kw)