. A little boy spits straight downward from the top of a 75 meter tall building. When the gob of spit leaves his mouth, it is traveling 15 m/s downward. how long does it take to reach the ground? how fast is it moving upon impact?

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.