Arifle with a longer barrel can fire bullets with a larger velocity than a rifle with a shorter barrel. a) explain this using the impulse-momentum theorem. b) explain this using the work-energy theorem

Africtionless piston-cylinder contains 50 l of saturated liquid r-134a. the piston has a mass and an area resulting in an applied pressure of 500 kpa on the refrigerant. the refrigerant is now heated until its temperature rises to 70∘c. calculate the work (in kj) done during this process.