Design an undamped vibration absorber such that the steady state amplitude of the primary mass is zero and the steady state amplitude of the absorber mass is less than 2 mm. the machine is 200 kg and it is attached to a spring with k 4x10 n/m. during its operation the machine is subjected to a harmonic excitation of 500 n at ω=50 rad/s

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?