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cfb
Bipolar (III) Inmate

From: Vancouver, WA
Insane since: Nov 2003

posted posted 06-10-2005 02:15

If somebody'd be willing to help, this problem has been bugging me and refuses to be solved. Although it should be easy, is easy, and is more emberassing to post than anything, seeing as it's a rudimentary physics problem meant to introduce electric fields, I could seriously use some help here. So if anybody has the time to waste, that'd be great.


Two charges Qx and Qy lie 6cm away from each other on a horizontal line. Directly between them and 4cm up (Qx+3cm, 4cm) (Qy -3cm, 4cm) lies point Z. Determine the magnitude and direction of the electric field at point Z due to the charges at Qx and Qy.

Qx, Qy = + 2.0 x 10^-8 C

I assume I'd calculate the electric field between Qx and Qy using Fe=(k*Qx*Qy) / (d^2), then input that into E = Fe / (r^2) to produce the answer, however nothing comes up with the book answer: 1.2 x 10^5 N/C [up]



(Edited by cfb on 06-10-2005 02:15)

(Edited by cfb on 06-10-2005 02:21)

templar654
Paranoid (IV) Inmate

From: beyond the WEB!
Insane since: Apr 2004

posted posted 06-10-2005 02:42

Electricity... next year for me!

cfb
Bipolar (III) Inmate

From: Vancouver, WA
Insane since: Nov 2003

posted posted 06-10-2005 04:00

Wow. That was simple; I think I was just momentarily hated by the Gods.

I forgot to treat it as a vector, so:

E = (k*Qx, Qy) / (d^2) = [k(2.0 x 10^-8)] / (.05^2) = 7.2 x 10^4 N/C [53.13 degrees]

and since the two forces are equal (Qx, Qy), they will negate the direction of pull/push, you can just input them into a sine/cosine law to get the answer, 1.2 x 10^5 N/C [90 degrees / up].

Sorry!

--------------------------------------------------------
"Abortion clinics are like expressways to heaven."

Tao
Maniac (V) Inmate

From: The Pool Of Life
Insane since: Nov 2003

posted posted 06-10-2005 04:31

Ah electrickery no less, glad you solved it cfb. I had the exact same answer
what?

::tao:::: ::cell::

White Hawk
Maniac (V) Inmate

From: zero divided.
Insane since: May 2004

posted posted 06-10-2005 14:18

Oh yeah - that's just child stuff. I was doing that in kindergarten...

ZZZZZZZZZZZZZZZZZZzzz....

cfb
Bipolar (III) Inmate

From: Vancouver, WA
Insane since: Nov 2003

posted posted 06-10-2005 16:37

Yeah, I was looking through the AP Physics and some college physics books. Oh my god! Reminds me of why I'm never, ever, pursuing a career in the sciences.

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