Now let’s apply Coulomb’s law and the superposition principle to calculate the force on a point charge due to the presence of other nearby charges. Two point charges are located on the positive x axis of a coordinate system. Charge q1=3.0nC is 2.0 cm from the origin, and charge q2 = -7.0 nC is 4.0 cm from the origin. What is the total force (magnitude and direction) exerted by these two charges on a third point charge q3=5.0nC located at the origin? A)In the same example, what is the magnitude of the force exerted on q1 by q2 and q3? b)In the same example, what is the direction of the force exerted on q1 by q2 and q3?

[tex]F_{13}=\dfrac{kq_1q_2}{r_{13}^2}\\\Rightarrow F_{13}=\dfrac{8.99\times 10^9\times 3\times 10^{-9}\times 5\times 10^{-9}}{0.02^2}\\\Rightarrow F_{13}=0.000337125\ N[/tex]

The force is 0.000337125 N towards -x axis

[tex]F_{23}=\dfrac{kq_3q_2}{r_{23}^2}\\\Rightarrow F_{13}=\dfrac{8.99\times 10^9\times -7\times 10^{-9}\times 5\times 10^{-9}}{0.04^2}\\\Rightarrow F_{23}=-0.00019665625\ N[/tex]

The force is 0.00019665625 N towards +x axis

Net force on [tex]q_3[/tex]

[tex]F=F_{13}+F_{23}\\\Rightarrow F=0.000337125-0.00019665625\\\Rightarrow F=0.00014046875\ N[/tex]

[tex]F_{31}=0.000337125\ N[/tex]

The force is 0.000337125 N towards +x axis

[tex]F_{21}=\dfrac{kq_1q_2}{r_{21}^2}\\\Rightarrow F_{13}=\dfrac{8.99\times 10^9\times -7\times 10^{-9}\times 3\times 10^{-9}}{0.02^2}\\\Rightarrow F_{23}=-0.000471975\ N[/tex]

The force is 0.000471975 N towards +x axis

Net force on [tex]q_1[/tex]

[tex]F=F_{31}-F_{21}\\\Rightarrow F=0.000337125-(-0.000471975)\\\Rightarrow F=0.0008091\ N[/tex]

The force is 0.0008091 N towards +x axis