Answer:
a)The third charge is placed at a distance of r=0.253 m from the charge of [tex]-1.1\ \rm \mu C[/tex] on right side of it
b) The third charge is placed at a distance of r=0.1762 m from the charge of magnitude [tex]4.9\ \rm \mu C[/tex] on its right side on x axis.
Explanation:
Given:
a)Let the The third charge is placed at a distance of r m from the charge of [tex]-1.1\ \rm \mu C[/tex] on right side of it. When one charge is positive and other charge is negative and net force on third charge is zero
[tex]\dfrac{4.9\times Q}{4\pi \epsilon_0(r+0.28)^2}=\dfrac{1.1\times Q}{4\pi \epsilon_0r^2}\\\\r=0.245\ \rm m[/tex]
b) If both charges are positive
Let The third charge is placed at a distance of r from the charge of magnitude [tex]4.9\ \rm \mu C[/tex] on its right side on x axis. then
[tex]\dfrac{4.9\times Q}{4\pi \epsilon_0(r)^2}=\dfrac{1.9\times Q}{4\pi \epsilon_0(0.28-r)^2}\\\\r=0.1726\ \rm m[/tex]