Step-by-step explanation:
It is given that,
Separation between the charges, r₁ = 2 m
Force between the charges, F₁ = 20 N
Separation between the charges finally, r₂ = 4 m
Let F₂ is the repulsive force. The formula for the repulsive force is given by :
![F=k(q_1q_2)/(r^2)](https://img.qammunity.org/2020/formulas/physics/high-school/uk8f4z91yssptetrk6ebnulp741i636gb7.png)
![(F_1)/(F_2)=(r_2^2)/(r_1^2)](https://img.qammunity.org/2020/formulas/physics/college/xmoy4y8gqcnja7h46yml1aox26zcgueb5n.png)
![(F_1)/(F_2)=(r_2^2)/(r_1^2)](https://img.qammunity.org/2020/formulas/physics/college/xmoy4y8gqcnja7h46yml1aox26zcgueb5n.png)
![F_2=(F_1r_1^2)/(r_2^2)](https://img.qammunity.org/2020/formulas/physics/college/gb39bftiosp5uqhf2fbweorvrqeyj4a52a.png)
![F_2=(20* 2^2)/(4^2)](https://img.qammunity.org/2020/formulas/physics/college/nmzwd07luwf1dvxkzuebfg794hvlbixp3c.png)
![F_2=5\ N](https://img.qammunity.org/2020/formulas/physics/college/nlvtsrrdm9lpaymnoqhn5hgmrrdd09nlez.png)
So, the repulsive force is 5 newton. Hence, this is the required solution.