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Rubentheran · Feb 11, 2011, 04:29 AM

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

ebaines · Feb 11, 2011, 07:02 AM

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.