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A small charged ball is hovering in the state of equilibrium at a height h over a very large horizontal uniformly charged sheet. If a disc of radius r < < h , is removed from the plate directly underneath the ball, then the acceleration of the ball will be

Options

  1. Ag 2 r h 2
  2. Bg 2 h r 2
  3. Cg 4 r h 2
  4. Dg 4 h r 2

Correct answer

A. g 2 r h 2

Step-by-step solution

Initially, m g = q E &#8658; q m = g E Now, a disc of charge Q = &#963; &#215; &#960; r 2 is removed. As r &#60; &#60; h , we can treat disc as a point charge. The acceleration of the ball is a = q Q 4 &#960; &#949; 0 h 2 m a = g 2 r h 2

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