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

Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 mpa and -10°c at a rate of 0.05 ka/s and leaves at 0.8 mpa and 50°c. the refrigerant is cooied in the condenser to 0.72 mpa and 26'c. it is then throttled to 0.15 mpa. sketch the t-s diagram for the system and evaluate: 6) the rate of heat removai from the refrigerated space (kw), it) the power input to the compressor (kw), ii) the isentropic efficiency of the compressor (%), and iv) the cop of the refrigerator.