- #1
Air_Gear
- 2
- 0
Homework Statement
A charge Q is at the origin. A second charge, Qx = 2Q, is brought to the point x = a and y = 0. A third charge Qy is brought to the point x = 0, y = a. If it takes twice as much work to bring in Qy as it did Qx, what is Qy in terms of Q?
Homework Equations
My main problem in this (Besides an incompetent professor ) is connecting the relationships of Qy, Qx, and Q, specifically Qy and Q. Also, I believe my formula for work to bring in a charge
(W = (k * Qx * Qy)/ R)
Might be wrong.
The Attempt at a Solution
W = work to bring in charge.
Wy = 2*Wx
Wx = (k * Q * Qx)/a => Wx = (k * 3Q)/a
Wy = (k * Q * Qy)/a
(k * Q * Qy)/a = 2 * (k * 3Q)/a => (k * Q * Qy)/a = (k * 6Q)/a
And here's where I start to have problems; constant 'k' and 'a' get canceled out, fine and dandy. However, the 'Q' also gets canceled out, which is bad as that's what I want my final answer in terms of.
Also, am I over thinking this, or do the vectors of Qy and Qx not allow me to make this connection?
Thanks to anyone can help, and I hope to have a pleasant stay here at Physics Help