# Problem 1

Contributed by Siddharth Tiwary (Indian Institute of Technology Bombay).

Two metal balls, both of mass $M$ and radius $R$ , are connected with a rigid dielectric weightless rod of length $L$ , assume that $L\gg R$ . The system is placed into a uniform external electric field of strength $E$ ; neglect gravity and friction forces. Find the period of small oscillations of this system around its stable equilibrium state.

Translation into Chinese

Please submit the solution of this problem via e-mail to physcs.cup@gmail.com. First hints will appear here on 24th November 2019, but after the publication of the first hint, the base score is reduced to 0.9 pts. For full regulations, see the “Participate” tab.