What could be done is to ask it at PhysicsSEPhysics. or Worldbuilding SE
That would improve the location of the question; however, you'd likely get downvoted at Physics there for lack of research, since it doesn't take much of an internet search to convert units to arrive at the equation set up and you then plug in the values. Someone at RPGSE was kind enough to do that for you.
One of the reasons that I offer you this answer is because Joules are not an in-game / in-universe unit. My initial response to the question when I first saw it in the review queue was something like what NautArch noted in the comment below this answer: what I saw was a word problem from a high school physics class rather than an RPG-related question.
Thanks for the comment reply on its rejection at Physics.SE.