Question

There is an insulator rod of length L and of negligible mass with two small balls of mass m and electric charge Q attached to its ends. The rod can rotate in the horizontal plane around a vertical axis crossing it ata distance L/4 from one of its ends. At first the rod is in unstabel equilbrium in a gorizontal umifrom electric field of field strenght E. Then we gently displace it from this position. Determine the maximim velocity attained by the ball taht is closer to the axis in the subsequent motion

Answer 1