Auniform, solid metal disk of mass 6.60 kg and diameter 21.0 cm hangs in a horizontal plane, supported at its center by a vertical metal wire. you find that it requires a horizontal force of 4.16 n tangent to the rim of the disk to turn it by 3.35 degrees, thus twisting the wire. you now remove this force and release the disk from rest.
(a) what is the torsion constant of the metal wire?
(b) what are the frequency and period of the torsional oscillations of the disk?
(c) write the equation of motion for the disk.

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)