HELP _7. All of the following except which would lead to an INCREASE in friction? A. string rubbing on wood
C. axles fitting very snuggly in axle holes
B. graphite powder
D. wheels tight against the wood side rails

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

Air (c-1.006 kj/kg.k, r-0.287 kj/kg.k) enters a nozzle steadily at 280 kpa and 77°c with a velocity of 50 m/s and exits at 85 kpa and 320 m/s. the heat losses from the nozzle to the surrounding medium at 20°c are estimated to be 3.2 kj/kg. determine (a) the exit temperature and (b) the total entropy change for this process. solve this problem using constant specific heats.

Around steel bar, made from material with a yield stress of 750mpa, is loaded so that it has stresses co locations of maximum normal stress and maximum shear stress. use maximum shear stress and maximum distortion energy theories to calculate the safety factors for initial yielding failures.