Aforce of 25.0 n is required to start a 3.0 kg box moving across a horizontal concrete floor. (a) what is the coefficient of static friction between the box and the floor? (b) if the 25.0 n force continues, the box accelerates at 0.50 m/s2. what is the coefficient of kinetic friction?

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)