Two 4.0 kg masses are 1.0 m apart on a frictionless table. Each has 1.0 μC of charge. What is the magnitude of the electric force on one of the masses?

Coulomb's law:

Force = (8.99*10⁹ N m² / C²) · (charge₁) · (charge₂) / distance²

= (8.99*10⁹ N m² / C²) (1 x 10⁻⁶ C) (1 x 10⁻⁶ C) / (1.0 m) ²

= (8.99*10⁹ x 1*10⁻¹² / 1.0) N

= 8.99*10⁻³ N

= 0.00899 N repelling.

Notice that there's a lot of information in the question that you don't need.

It's only there to distract you, confuse you, and see whether you know

what to ignore.

- - '4.0 kg masses'; don't need it.

Mass has no effect on the electric force between them.

- - 'frictionless table'; don't need it.

Friction has no effect on the force between them,

only on how they move in response to the force.