For a direct shear test on a cohesionless sand, the following are given: - Size of specimen: 75 mm x 75 mm x 30 mm (height) - Normal stress: 200 kPa - Shear stress at failure: 175 kPa Determine a) the angle of friction, and b) the required shear force that cause failure in the specimen if normal stress is 150 kPa

Explain the difference laminar and turbulent flow. explain it with the shear stress and the velocity profiles.

Apiston-cylinder with a volume of 0.25 m3 holds 1 kg of air (r 0.287 k/kgk) at a temperature of 100 c. heat transfer to the cylinder causes an isothermal expansion of the piston until the volume triples. how much heat is added to the piston-cylinder?

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?