When a bow is stretched back and an arrow is shot, what type of energy conversion has occurred?
a. chemical to mechanical
b. elastic to mechanical
c. mechanical to thermal
d. mechanical to elastic

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.