Airflow through a long, 0.1-m-square air conditioning duct maintains the outer duct surface temperature at 15°c. if the horizontal duct is uninsulated and exposed to air at 35°c in the crawlspace beneath a home, what is the heat gain per unit length of the duct? evaluate the properties of air at 300 k. for the sides of the duct, use the more accurate churchill and chu correlations for laminar flow on vertical plates.

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.