Question #42844

An elevator is accelerating vertically upwards with a constant acceleration $a$. Inside the elevator, an infinite flat non-conducting sheet with a uniform positive surface charge density $\sigma$ is fixed vertically. A rigid, rough, non-conducting vertical rod is fixed parallel to the sheet at a distance $d$ from it. A bead of mass $m$ and positive charge $q$ is threaded on the rod. The coefficient of kinetic friction between the bead and the rod is $\mu$. If the bead is released from rest relative to the elevator, what is its kinetic energy relative to the elevator after it has slid a distance $L$ down the rod? (Assume $m(g+a) > \frac{\mu q \sigma}{2\varepsilon_0}$ and neglect edge effects).