An object moves in a circle of radius R at constant speed with a period LaTeX: T T
. By what factor should the period be changed so that the object's final acceleration magnitude is LaTeX: k
k
times its initial value (that is, LaTeX: a_f=k\,a
a
f
=
k
a
) where LaTeX: k=
k
=
0.553.

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.