Your company design and manufacture engineering polymers with outstanding mechanical properties. During a quality control test, a 25.0-cm-long polymer sample is stretched with a constant tensile load of 20.0 kPa, it stretches to a total length of 37.5 cm in 1200 s. After removing the load, the sample recovers only to 26.75 cm. Assuming that the mechanical behavior of the polymer can be treated as a Maxwell element, estimate the time it would take for an identical (untested) sample to relax to 0.750 its original stress when a constant elongation of 50% is applied.

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?

Vibration monitoring this technique uses the noise or vibration created by mechanical equipment and in seme cases by plant systems to detemine their actual condtion. a)- true b)- false

Agas mixture consists of 8 kmol of h2 and 2 kmol of n2. determine the mass of each gas and the apparent gas constant of the mixture.