The original magnitude of the force on the q charge was f; what is the magnitude of the force on the q charge now?

Complete Question:

Two small objects each with a net charge of Q (where Q is a positive number) exert a force of magnitude "F" on each other. We

replace one of the objects with another whose net charge is 4Q. The original magnitude of the force on the Q charge was "F"; what is the magnitude of the force on the Q charge now?

4 F₀

Explanation:

Assuming that we can treat to both objects as point charges, we can find the force "F" that one charge exerts upon the other applying Coulomb´s law, as follows:

F₀ = K*Q₀² / r₁₂²

If we replace one of the charges by one with a 4Q₀ charge, the new value of F will be as follows:

F₁ = K*Q₀*4Q₀ / r₁₂² =( K*Q₀² / r₁₂²)* 4 = 4* F₀

This value is reasonable, as the electrostatic force is a linear - type one, so it is possible to use the superposition principle (we can get the force exerted by one charge on another without considering the ones due to another charges)