Question

Which one of the following objects is in equilibrium? (Could someone give reasoning on the answer?)

A. A stone trapped in the tread of a rotating tyre. B. An air molecule as a sound wave passes through the air. C. A steel ball falling at constant speed through oil. D. An electron moving through a metal under the action of a potential difference.

Ans from sheet: D

Answer 1

D. An electron moving through a metal under the action of a potential difference.