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.

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Distance covered, s = 8ft - 4ft = 4 ftinitial velocity, u = 34 ft/sthe acrobat is moving upwards and therefore, a = -g = -9.81 m/s^2 = 32.19 ft/s^2applying equation of motion; s = ut -1/2gt^2then,4 = 34t -1/2*32.19t^24 = 34t - 16.095t^2rearranging; -16.095t^2 + 34t - 4 = 0solving the quadratic equation; t = {-34 +/- sqrt [34^2 - 4(-16.)]}/2(-16.095) = 1.06 +/- 0.93 = 0.13 or 1.99the acrobat will take 0.13 seconds to be at 8 ft above the ground. additionally, once at the maximum height, the acrobat will move down and be at the same spot (that is height) after 1.99 seconds moving down.