<span>The first choice i correct. The second is also correct as it should obey the Law of Conservation of mass. The third choice is incorrect. It depends on the nature of the system. For example, for an ideal gas, you can define at least 2 parameters to set the system boundaries. The fourth choice is incorrect, a system can be theoretical or practical. Hence, the answers are the first and second choices.</span>
Part a) The work done by the gas on the bullet is the integral of the force in dx, where x is the distance covered by the bullet inside the barrel with respect to the origin: By substituting the length of the barrel, L=0.540 m, we find the total work done by the gas on the bullet:
part b) The resolution of the problem is the same, we just have to use the new length of the barrel (L=0.95 m) inside the final formula, and we find the new value of the work: