Aflexural member is fabricated from two flange plates 1/2x16 and a web plate 1/4x20. the yield stress of the steel is 50 ksi.
a. compute the plastic section modulus z and the plastic moment mp with respect to the major axis.
b. compute the section modulus s and the plastic moment my with respect to the major axis.

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?