Answer: 34.65 N towards charge 8 μC.
Step-by-step explanation:
The electrostatic force between two charges is given by:
![F =k (q_1q_2)/(r^2)](https://img.qammunity.org/2020/formulas/physics/middle-school/ebbu2cpbi2rkywwuz90jez8er59vp9sftm.png)
where, k is the Coulomb constant = 8.9875 × 10⁹ N.m²/C²
q₁ and q₂ are the two charges separated by distance r.
The distance between charges 8 μC and -7 μC is r = 2 cm -(-10 cm) = 12 cm = 0.12 m
The force between these charges is:
![F = 8.9875 * 10^9 Nm^2/C^2 * (8* 10^(-6)C* (-7*10^(-6)C))/((0.12m)^2) = -34.95 N](https://img.qammunity.org/2020/formulas/physics/middle-school/69ipndpcsuyt4pvgm7uonoyls2aahepy5d.png)
Negative sign implies it is an attractive force.
The distance between -3 μC charge and -7 μC charge is r' = 10 cm -2 cm = 8 cm = 0.8 m.
The electrostatic force between these charges is:
![F' = 8.9875* 10^9Nm^2/C^2* ((-3 * 10^(-6)C)* (-7* 10^(-6)C))/((0.8m)^2) = 0.295 N](https://img.qammunity.org/2020/formulas/physics/middle-school/ivqpvdshc7ifrfuycy40qsg36kaafb9o5c.png)
It is a repulsive force.
Net force on the -7 μC charge is:
Fn = F + F'
we can add them directly as they are acting in one direction along the x-axis.
Fn = -34.95 N + 0.295 = -34.65 N
Thus, the net force is attractive in nature and it is towards charge 8 μC.