Final answer:
To nullify the net electrostatic force on a third charge (q3) along the x-axis due to q1 and q2, position q3 at x3 = 4.0 cm. therefore correct answer is option a.
Step-by-step explanation:
To find the position where a third charge should be placed on the x-axis so that the total electrostatic force acting on it is zero, we need to consider the electric forces exerted by q1 and q2 on q3.
The electric force between two point charges is given by Coulomb's law:
F = k * (q1 * q2) / r²
Where F is the force, k is the Coulomb's constant, q1 and q2 are the charges, and r is the distance between the charges.
To find the position where the total electrostatic force on q3 is zero, we need to set up an equation equating the forces exerted by q1 and q2:
k * (q1 * q3) / (x3 - x1)² = k * (q2 * q3) / (x2 - x3)²
Simplifying and solving for x3, we find that x3 = 4.0 cm.