Determine the force of interaction between 2 electric charges q1= 1x10-6 C and q2= 2x10-6 C at the distance r = 2 m.

Question

I think the formula is F=kq1*q2/r2? How do I find k?

Answer 1

You either look k up
k = 9 * 10^9 N m^2/C^2
or you know it is
1/(4 pi eo)
and you know eo = 8.8 * 10^-12 C^2/(N m^2)

Answer 2

You do not find k, you memorize it in SI units.
k= 8.987E9 N.m^2/C^2