Van der Waals and electrostatic force between polystyrene spheres

Mr.A.Gibson

1. The problem statement, all variables and given/known data

Compare gravitational, electrostatic and van der Waals forces between two 100nm polystyrene spheres which are separated by a) one micrometer b) one millimetre and c) one centimetre

2. Relevant equations

Gravitation and electrostatic equations are standard.

3. The attempt at a solution

After looking up a reasonable density of polystyrene, the gravitational force is easy to calculate.

Surely the electrostatic force is zero, as no charge is mentioned in the question. Also surely Van der waals force is zero at this sort of distance. But I have a feeling I'm missing something any ideas?