An 8-m-long, uninsulated square duct of cross section 0.2 m x 0.2 m and relative roughness 10^-3 passes through the attic space of a house. hot air enters the duct at 1 atm and 80°c at a volume flow rate of 0.15 m^3 /s. the duct surface is nearly isothermal at 60°c. determine the rate of heat loss from the duct to the attic space and the pressure difference between the inlet and outlet sections of the duct. evaluate air properties at a bulk mean temperature of 80°c. is this a good assumption?

Explain the difference laminar and turbulent flow. explain it with the shear stress and the velocity profiles.

The force on a cutting tool are 2600n vertically downward and 2100 horizontal. determine the resultant force acting on the tool and the angle at which it acts.

Ajournal bearing has a journal diameter of 3.250 in with a unilateral tolerance of 20.003 in. the bushing bore has a diameter of 3.256 in and a unilateral tolerance of 0.004 in. the bushing is 2.8 in long and supports a 700-lbf load. the journal speed is 900 rev/min. find the minimum oil film thickness and the maximum film pressure for both sae 20 and sae 20w-30 lubricants, for the tightest assembly if the operating film temperature is 160°f. a computer code is appropriate for solving this problem.