Final answer:
The magnitude of the Coulomb force on a charge 3Q is three times the magnitude of the Coulomb force on a charge Q.
Step-by-step explanation:
The magnitude of the Coulomb force between two point charges can be calculated using Coulomb's law, which states that the force is given by the equation F = k|qQ|/r², where F is the magnitude of the force, k is the electrostatic constant, q is the charge of the first point charge, Q is the charge of the second point charge, and r is the distance between the charges.
In this scenario, we have a point charge Q and a point charge 3Q. If the magnitude of the Coulomb force on Q is F, the magnitude of the Coulomb force on 3Q can be calculated using the same equation. However, since the charge of 3Q is three times the charge of Q, the magnitude of the force on 3Q will be three times the magnitude of the force on Q. Therefore, the magnitude of the Coulomb force on 3Q is 3F.