a 16kg child on roller skates, initially at rest, rolls 2.0 m down an incline at an angle of 20 degrees with the horizontal. if there is no friction between incline ans skates, what is the kinetic energy of the child at the bottom of the incline

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.