Can Coulomb force be negative?

Hint: You could first recall the quantities that experience Coulomb force. Then, you could think of all the known possibilities of that force being negative. You could then mathematically express coulomb’s law to get better understanding. Thereby, you will get the answer to the given question.

Complete answer:
In the question, we are asked whether coulomb force can be negative. Coulomb force, if you may recall, is the force between two charges. We know that we have two types of charges in the universe. One which is positive and other that is negative. We have another universal fact that like charges repel and unlike charges attract. The force between two like charges is repulsive and unlike charges is attractive.
We know the statement of Coulomb’s law. Coulomb’s law states that the force between two charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. Mathematically, we could give this expression along with the proportionality constant as,
$F=k\dfrac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}$
Quite clearly we see that the resulting force will be negative when one of the charges is negative and the other is positive. That is, the Coulomb force between opposite charges is negative.
Therefore, we found that Coulomb force can be negative.

Note:
Normally negative defines the direction. But here the negative sign doesn’t give the absolute direction. However, we get to say whether the force is acting towards or away from each other. So, the coulomb force is negative when the force is towards each other and positive for repulsive force.