How can they remove same amount of energy via drag when they have different magnitude of drag? Did the initial question state that they have same drag?
It doesn't, its an implied boundary condition
But i can produce exactly the same question using fluids, thermo, dynamics and statics as the base line which is why we used this "problem" as an example for undergrads. I had to make them up to teach the fact that system means nothing when looking at a problem. I have exactly the same problem for each perversion including electrical using exactly the same energy conversions. I.e potential to some system which has a disapation factor.
It doesn't matter your perversion the energy freebody diagram will give the solution to the relationship.
Before I go any futher do you actually know what a free body diagram is and how engineers use it to simulate systems? Or for that matter what a boundary condition is?