Posted by Char on .
Particles 1 and 2 of charge q1 = q2 = +3.20 x 1019 C are on a y axis at distance d = 22.0 cm from the origin. Particle 3 of charge q3 = +9.60 x 1019 C is moved gradually along the x axis from x = 0 to x = +5.0 m.
At what value of x will the magnitude of the electrostatic force on the third particle from the other two particles be maximum?
What is the maximum magnitude?

Physics  please help! 
drwls,
Is particle 2 at x = 0, y = 22 cm?
If so, the net force on P3, F3, is always along the x axis, and is zero at x=0.
F3 = 2*k*q1*q3*x/(x^2 + a^2)^3/2
where a = 22 cm
Maximum force occurs where dF3/dx = 0
I get it to be where x = 22 cm/sqrt2 = 15.55 cm
See what you get, and use the equation above to get the maximum force F3