Consider a square flat plate at zero incidence angle to a low-speed incompressible flow. the length of each side is 4 m. assume that the transition reynolds number is 5 × 105 and that the free-stream properties are those at standard sea level. calculate the friction drag on the flat plate when the free-stream velocity is
(a) 20 m/s and when it is
(b) 40 m/s.
(c) assuming that the friction drag, df, varies with velocity as , calculate the value of the exponent n based on the answers from (a) and (b). how close does n come to 2? that is, how close is the friction drag to obeying the velocity squared law?

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?