The ball will oscillate along the $z$ axis between $z=d$ and $z=-d$ in simple harmonic motion. What will be the angular frequency $$ of these oscillations? Use the approximation $da$ to simplify your calculation; that is$,$ assume that $d^2+a^2$~~$a^2.$ Express your answer in terms of given charges, dimensions, and constants. View Available Hint$($s$)=$