This is roughly High School level physics (basic, not AP or any honors or anything).
In this particular case, there's the knowledge of the first basic law of thermodynamics (You can't win, the limiting case on energy conversion) and Kinematics, typically taught as the first half/third of physics. (Broadly: Mechanics/Kinematics, E/M, Optics and Waves)
In most physics courses, you’ll hit conservation of energy even before it’s presented in thermodynamics packaging. This kind of calculation should be less than a week’s worth of casual effort for someone who is familiar with algebra.
In this particular case, there's the knowledge of the first basic law of thermodynamics (You can't win, the limiting case on energy conversion) and Kinematics, typically taught as the first half/third of physics. (Broadly: Mechanics/Kinematics, E/M, Optics and Waves)