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?
Answer:
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)
