1.Three +20 uC charges are placed on a straight line, successive charges being 2 m apart as shown in Figure 1.Calculate the force on the right end.

I couldn't get the answer right.I got 10,000 N which is way out.I used the formula F=eV.Can someone give solution for this question
Image is attached on this question.Given answer for this question is

Ans:1.125 N and points to the right


uC= u represents micro(I wrote u because I cannot write the symbol for micro in here)

Someone please help me.Thanx in advance

You are using the wrong formula. The elecrostatic force between charged particles is calculated using Coulomb's law:


F = k_e \frac {q_1 q_2}{d^2}


So here you have


F_{total}= F_1 + F_2 = k_e \frac {q^2}{d_1^2}+k_e \frac {q^2}{d_2^2}
= k_e (20 \times 10^{-6} C)^2 (\frac 1 {(2m)^2}+ \frac 1 {(4m)^2})


Where


k_e = 8.987 \times 10^9 \frac {N m^2}{C^2}


Try it again and post back what you get.