Diver uses a sonar device to determine the distance to her diving partner. the device sends a sound wave and records the time it takes for the wave to reach the diving partner and return to the device. suppose the wave travels at a rate of about 4000 feet per second. the wave returns 0.8 second(s) after it was sent. how far away is the diving partner?

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.