Which of the following involves the emission of a particle that has the same mass of an electron with a positive charge.
a. alpha decay
c. positron emission
b. beta decay
d. nuclear forces

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.