An explosion occurs at the end of a pier. the sound reaches the other end of the pier by traveling through three media: air, fresh water, and a slender metal handrail. the speeds of sound in air, water, and the handrail are 339, 1480, and 5060 m/s, respectively. the sound travels a distance of 141 m in each medium.

(a) after the first sound arrives, how much later does the second sound arrive?
(b) after the first sound arrives, how much later does the third sound arrive?

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)