In a certain binary-star system, each star has the a mass of 1.20 1030 kg, and they revolve about their center of mass. The distance between them is 2.0 108 km. What is their period of revolution in Earth years?

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.