Question

if q1q2>0, what can we say about the nature of the force?

Answer 1

By coulomb's law
F =  1/ 4πε₀ × q₁q₂/ r² 
when q₁q₂ is greater dan 0  , it means q₁ &  q₂ will either +ve / -ve 
As if they both hav same kind of charge it will be a repulsive force.......
Thus, the electrostatic force experience will be REPULSIVE.....

Answer 2

Since, q1q2 >0, that means both charge having same nature, that means either both positive or both negative and we know that like charges repel each other. So, the nature of force will be repulsive.