Which of the following are hazards associated with portable ladders? A) Ladder is not positioned correctly

B) Ladder is too long

C) Ladder is not tied off correctly

D) Unsteady ladder

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?

What is a monomer? how do they form a ploymer from the view point of chemical bonding?

When subject to a steady load (within elastic range) over a long period of time, what is the major difference in material behavoir between steel and plastic?