Final answer:
When the distance between two point charges is doubled, the electrostatic force becomes 1/4 of the original force. Therefore, if the initial force was 9 x 10, the new force would be 2.25 x 10.
Step-by-step explanation:
The student's question involves the concept of electrostatic force as explained by Coulomb's law, which calculates the force between two point charges. According to Coulomb's law, the electrostatic force (F) between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. If the initial force between two point charges 1.0 m apart is 9 x 10N and the distance is doubled, the new distance between the charges becomes 2.0 m.
Using Coulomb's law, if the distance between charges is doubled (r becomes 2r), the force is reduced by a factor of 22 or 4, because the force varies inversely with the square of the distance. Therefore, the new force would be 1/4 of the original force.
To find the new magnitude of the force, we divide the initial force (9 x 10N) by 4. The new force between the point charges when the distance between them is doubled would then be 2.25 x 10N.