Final answer:
To determine the charge Q, use Coulomb's law and set up two equations using the given information. Solve the equations to find Q.
Step-by-step explanation:
To determine the charge Q, we can use the concept of electric force between charges. The force between two charges is given by Coulomb's law:
F = (k * Q1 * Q2) / r^2
Where F is the force, k is the electrostatic constant, Q1 and Q2 are the charges, and r is the distance between the charges.
Using the given information, we can set up two equations and solve for Q:
At x = 4.0 cm, the force is zero, so:
0 = (k * Q * (-7μC)) / (4.0 cm)^2
At x = 8.0 cm, the force is 674 N, so:
674 N = (k * Q * (-7μC)) / (8.0 cm)^2
Solving these equations will give us the value of Q.