Ian G.

# Physics Gaussian Law

A thin conductive sheet is placed on the ground. The sheet is square with L m side
length and carries a total charge of Q C. A small ball bearing is held above the centre of the
sheet and carries a charge of q C. The ball bearing can be considered as a point charge with a
mass of m kg. The sheet can be considered as infinite in extent compared with the bearing.

1) Derive the mass of the ball bearing that will allow it to levitate above the
conductive sheet.

2) If the bearing is held at the surface and released, calculate its initial acceleration in
the vertical direction. Neglect both gravity and air resistance in this case.

Q =25 C q = 1 x 10-3 C  L= 100 m   and m =10g

For part 1 I am sure its equating 2 forces and solving for m? Not 100% sure.

No idea how to do part 2)

Thanks

Ian

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