Hi, I am having trouble with these two Physics problems. I know that you have to

Question

Hi,

I am having trouble with these two Physics problems. I know that you have to use the quadratic formula, but I am not sure if my set up has been correct or maybe I am not solving it correctly. I would appreciate some help, since I have been on this problem for a while, and have spent at least over an hour trying to solve it.

Zero E Field A positive point charge Q1 = 3.96E-5 C is fixed at the origin of coordinates, and a negative charge Q2 =-3.45E-6 C is fixed to the x axis at x = +2.13 m. Find the location of the place along the x axis where the electric field due to these two charges is zero. 3.02 m Submit Answer Incorrect. Tries 2/10 Previous Tries

Explanation / Answer

By kQ1 / x^2 = kQ2 / (x +2)^2

k = 9x10^9, Q1 = 3.96x10^-5 and Q2 = -3.45x10^-6

=>  9x10^9 *  3.96x10^-5 /x^2 = 9x10^9 * -3.45x10^-6/(x+2.13)^2

=>356400/x^2 = -31050 / ( x^2 + 4.53)

=> 2.04m

part c)

Now k*Q1*Q2/r12^2 = k*Q2*Q3/x^2

simplifying we get Q1/r12^2 = Q3/x^2

so x = r12^sqrt(Q3/Q1)

= 0.290*sqrt(3.03x10^-6/1.56x10^-6) = 0.4041m

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