6 years ago you asked about the origin of the (-) in the differential equation for the RC Circuit. I felt compelled to make an account & tell you that the last lecture note that my physics professor posted for the year was based on this question, and he used it as lesson on perseverance and the desire for learning. There was even a heading titled Simpcar: an Internet Hero. I disclosed the lecture note in a private message to you; I added this post just to increase the likelihood of you seeing it