Final answer:
A student asked about the net force on a -25 µC charge placed exactly halfway between +85 µC and -70 µC charges. By applying Coulomb's Law, the attraction and repulsion forces cancel each other out, resulting in a net force of zero.
Step-by-step explanation:
The question is about the net force on a third charge placed exactly halfway between a +85 µC charge and a -70 µC charge. The third charge is -25 µC. According to Coulomb's Law, the force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. Since the third charge is equidistant from both the positive and negative charges, the forces due to each will be of the same magnitude but opposite in direction.
The force exerted on the -25 µC charge by the +85 µC charge will be an attraction force, while the force exerted by the -70 µC charge will be a repulsion force. The magnitude of these forces will depend on the respective products of the charges and the distance squared, but since the third charge is exactly halfway, the distances are equal, rendering the magnitudes of attraction and repulsion forces the same but in opposite directions. Therefore, the net force on the -25 µC charge will be zero due to the perfect cancellation of the two forces.