Hi, I'm a bit confused about the solution of this question. Assuming w and B are as defined and R = Ee, there isn't really a force that depends on v, so one way to obtain the answer is simply to set the sum of all forces equal to 0 and solve for e. Even if we were to set up a differential equation, the equation would only involve v' and some constants, and the solution is trivial. Is this what is expected in this question?

Any help is appreciated. Thank you!