A laminar boundary layer is formed on one side of a plate of length L produces a drag D. How much must the plate be shortened if the drag on the new plate is to be D/4? Assume the upstream velocity remains the same. Explain your answer physically.

The higher the astm grain-size number, the coarser the grain is. a)-true b)-false

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.

The process in which the system pressure remain constant is called a)-isobaric b)-isochoric c)-isolated d)-isothermal