Answer:
0.7 N
Explanation:
q1 = 7 micro coulomb
q2 = - 3 micro coulomb
distance = r
Force, F = 3.7 N
Let the new force be F'.
By use of Coulomb's law
[tex]F=\frac{Kq_{1}q_{2}}{r^{2}}[/tex]
[tex]3.7=\frac{K\times 7\times 10^{-6}\times 3\times 10^{-6}}{r^{2}}[/tex] .... (1)
Now touch the spheres,
q1 = q2 = (7 - 3 )/ 2 = 2 x 10^-6 C
Now
[tex]F'=\frac{K\times 2\times 10^{-6}\times 2\times 10^{-6}}{r^{2}}[/tex] .... (2)
Dividing equation (2) by equation (1), we get
[tex]\frac{F'}{3.7}=\frac{4}{21}[/tex]
F' = 0.7 N
Thus, the new force is 0.7 N.