An empty office chair is at rest on a floor. Consider the following forces:
1. A downward force due to gravity;
2. An upward force exerted by the floor; and
3. A net downward force exerted by the air.
Which force(s) act on the office chair?

What is the temperature in degrees celsius of a substance with a tempature of 49k

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)

Which of these activities increases the amount of carbon in the atmosphere?