Problem 11-35 Potential and kinematics - Part 4B - B

A proton is accelerated from rest from a positively charged plate to a parallel negatively charged plate. The separation of the plates is \(8.9\; mm.\) If the potential difference between the plates is \(75.3\; V,\) what is the speed of the proton just as it hits the negative plate?
[Ans. \(1.2 \times 10^5\; m/s\)]

Accumulated Solution

Proton diagram B

\(U = qV \\ E_{K1} + U_1 = E_{K2} + U_2\)

Correct!

What are the correct values of \(E_K\) and \(U\)?

Solution \(E_{K1}\) \(U_1\) \(E_{K2}\) \(U_2\)
(A) 0 \(q\Delta V\) \(½ \;mv_2{^2}\) 0
(B) 0 0 \(½ \;mv_2{^2}\) \(-q\Delta V\)
(C) 0 0 \(½ \;mv_2{^2}\) \(q\Delta V\)
(D) 0 \(-q\Delta V\) \(½ \;mv_2{^2}\) 0