To find the point where the total electric field is equal to zero, we can use the principle of superposition, which states that the electric field at a point due to multiple point charges is equal to the vector sum of the individual electric fields at that point.
First, we need to determine the direction of the electric fields at the point in question. We know that electric fields point away from positive charges and towards negative charges. In this case, q1 is positive and q2 is negative, so the electric fields will be pointing in opposite directions.
Next, we can use Coulomb's law to find the magnitude of the electric fields at the point. Coulomb's law states that the electric field at a point due to a point charge is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the point charge and the point in question.
In this case, we have two point charges, so we need to find the electric field due to each charge separately and then add them together. The equation for the electric field due to a point charge is E = kq/r^2, where k is the Coulomb's constant (8.99 x 10^9 Nm^2/C^2), q is the magnitude of the charge, and r is the distance between the charge and the point in question.
For q1, the distance is 1.20m, so the electric field would be E1 = (8.99 x 10^9 Nm^2/C^2)(0.50 x 10^-9 C)/(1.20m)^2 = 3.12 x 10^-4 N/C.
For q2, the distance is also 1.20m, but the charge is negative, so the electric field would be E2 = (8.99 x 10^9 Nm^2/C^2)(-8.00 x 10^-9 C)/(1.20m)^2 = -3.12 x 10^-3 N/C.
Now, we can add these two electric fields together to find the total electric field at the point. Since the fields are pointing in opposite directions, we can subtract the magnitudes to find the net electric field.
Etot = |E1| - |E2| = (3.12 x 10^-4 N/C) - (3.12 x 10^-3 N/C) =