A positively charged disc is placed on a horizontal plane. A charged particle is released from a certain height on its axis. The particle just reaches the centre of the disc. Select the correct alternative.

Options

A. particle has negative charge on it
B. total potential energy (gravitationl+electrostatic) of the particle first increases, then decreases
C. total potential energy of the particle first decreases, then increases
D. total potential energy of the particle contilnously decreses

Answer

C

Explanation

Hence, in between A and C there is a point B, where speed of the particle should be maximum.
`F_1=mg=constant`
`F_2=` electrostatic repulsion (which increases as the particle moves down)
From A to B kinetic energy of the particle increases and potential energy decreases. Then from B to C kinetic energy decreases and potential energy increases