The best evidence for a black hole at the center of the galaxy also comes from the application of kepler’s third law. suppose a star at a distance of 20 light-hours from the center of the galaxy has an orbital speed of 6200 km/s. how much mass must be located inside its orbit?

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.