Answer True of False to the following statements.

a. Above its glass transition temperature, a polymer is glassy and brittle.
b. Below the glass transition temperature, polymer chains lose their mobility (they are less capable of bending, flexing, raveling, and rotating about covalent bonds along the backbone.
c. The glass transition temperature of a material is normally above its melting temperature.
d. The elastic modulus of a polymer decreases when it is heated above its glass transition temperature

Steel is coated with a thin layer of ceramic to protect against corrosion. what do you expect to happen to the coating when the temperature of the steel is increased significantly? explain.

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false

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?