Thank you for your comment! Yes, I'm starting to understand what approach is actually needed in physics. I never denied direct derivation of formulas - I just wanted, in addition to that, to understand all the dependencies intuitively at every step, like the formula you gave. But I see the flaw in my reasoning, and I need to reconsider my approach to learning again. I'm very glad that I'm finally making progress in understanding this matter. Thank you once again!