Final answer:
The relationship between electrostatic force and distance for two oppositely charged spheres is that the force follows an inverse square law, increasing sharply as distance decreases and decreasing when the spheres are farther apart.
Step-by-step explanation:
When two oppositely charged metal spheres are brought toward each other, the electrostatic force exerted between them follows an inverse square law, which means that the force is inversely proportional to the square of the distance between their centers. Thus, as the distance between the spheres decreases, the electrostatic force increases sharply. If they are moved further apart, the force decreases. This relationship can be represented graphically, where the force would decrease as the square of the increase in distance, forming a curve that rapidly descends as we move from left to right on the graph of electrostatic force versus distance.