An aircraft fuselage is 180" in diameter to the midplane of the skin, which is 0.063" thick 7075-t6 al sheet (ftu-79 ksi, e-10.5 msi). if the aircraft is pressurized each flight to a maximum differential pressure of 9.1 psi, and a factor of safety of 2.0 is required for evaluating static strength against ultimate pressure, assume the skins carry the pressure load alone (frame assistance is negligible) & determine the maximum ultimate principal stresses in the skin, and the minimum ultimate (static) margin of safety 1 . fi-26.0 ksi, f2=13.00 ksi, ms-2.04.

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

Apipe with an outside diameter of 15 cm is exposed to an ambient air and surrounding temperature of -20°c. the pipe has an outer surface temperature of 65°c and an emissivity of 0.85. if the rate of heat loss from the pipe surface is 0.95 kw per meter of length, the external convective heat transfer coefficient (h) is: (a) 12.5 w/m"k (b) 18.6 w/mk (c) 23.7 w/mk (d) 27.9 w/mk (e) 33.5 w/mk

Burgers vector is generally parallel to the dislocation line. a)-true b)-false