Answer:
The value of q is
![(Q)/(8)](https://img.qammunity.org/2021/formulas/physics/college/1hjy8men1kjv35xfzl9fkxrl20vl2ojso1.png)
Step-by-step explanation:
Given that,
Each charge = -Q
Distance between charges = L
Reduced force =
![(F)/(2)](https://img.qammunity.org/2021/formulas/physics/college/mv6piieg8go1zzkdu1025c3kzsc3gvdmiu.png)
Suppose, Two particles each with a charge -Q are fixed a distance L apart as shown above. Each particle experiences a net electric force F. A particle with a charge +q is now fixed midway between the original two particles.
We know that,
The force on each end is
...(I)
If the charge q is placed at mid point then
The force on each end charge is
....(II)
We need to calculate the value of q
Using equation (II)
![(F)/(2)=F+F'](https://img.qammunity.org/2021/formulas/physics/college/1fmh9alo3rlvsg420omzapryvhrufdlbkr.png)
Put the value of F into the formula
![((kQ^2)/(L^2))/(2)=k(Q^2)/(L^2)+k(q*(-Q))/(((L)/(2))^2)](https://img.qammunity.org/2021/formulas/physics/college/6q0b61r9s53ye8gxglh0aealh5aucotva5.png)
![(kq(-Q))/(((L)/(2))^2)=-(kQ^2)/(2L^2)](https://img.qammunity.org/2021/formulas/physics/college/arji2ow73m7817njcatheqwlxjbgassp7h.png)
![(q)/((1)/(4))=(Q)/(2)](https://img.qammunity.org/2021/formulas/physics/college/v3tb6lzo6h780ojdfa9iz1c3wivgqgyix0.png)
![q=(Q)/(8)](https://img.qammunity.org/2021/formulas/physics/college/j8h1gwhkth2p3ajm269mrol9195d4x7jt8.png)
Hence, The value of q is
![(Q)/(8)](https://img.qammunity.org/2021/formulas/physics/college/1hjy8men1kjv35xfzl9fkxrl20vl2ojso1.png)