Object dropped from height of 25 meters, what velocity will it hit the ground?

What color of light must blue light mix with to create white light? a. yellow b. white c. blue d. green

Anybody wanna ? (picture included? )

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.