What particles of an atom are inside the neuculas?

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

Work = force × a. work b. energy c. distance d. momentum

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.