A nonconducting disk of radius a and uniform positive surface charge density `sigma` is placed on the ground, with its axis vertical. A particle of mass m and positive charge q is dropped, along the axis of the disk, from a height H with zero initial velocity. The particle has `q//m = 4 epsilon_(0) g// sigma`.
(i) Find the value of H if the particle just reaches the disk.
(ii) Sketch the potential energy of the particle as a function of its height and find its equilibrium position.

Explanation

To solve the problem step by step, we will break it down into two parts as per the question.

### Part (i): Finding the value of H if the particle just reaches the disk

1. **Understanding the System**:
- We have a non-conducting disk of radius \( a \) with a uniform positive surface charge density \( \sigma \).
- A particle of mass \( m \) and charge \( q \) is dropped from a height \( H \) with zero initial velocity.

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