- #1
Rijad Hadzic
- 321
- 20
Homework Statement
https://imgur.com/gallery/YwCap
In side are image of figure, and questions.
Homework Equations
E = kq/r^2
The Attempt at a Solution
So I have an electric field where the y compontents cancel.
I have [itex]2Ecos(∂) = E (Electric field at point A) [/itex]
- 2 because there is a top and bottom part of rod with same magnitude.
- Electric field formula product cos(greekletter) to get the x component only
I have [itex]E = kQ/R^2 [/itex]
big R because that's the radius given, and it will never change.
[itex] Q/L = \Lambda, dQ = dL\Lambda [/itex]
Okay now here is where I'm confused...
I can set [itex] dL = R*d(∂)[/itex], right? Because essentially that is the arclength, right?!?
[itex] dQ = R*d(∂) * \Lambda [/itex]
so [itex] dE =( R*d(∂) * \Lambda * k ) / R^2 [/itex]
pull out constants
E = (R * lambda * k ) / R^2 * integral of d(∂), from 0 to R∂, (the acrlength of the rod)
So now you have
[itex]E = R^2 * \Lambda * k * ∂ / R^2 [/itex]
but [itex] Q = \Lambda * ∂ * R [/itex]
[itex] E = Q*R*k / R^2 [/itex]
[itex]E = Q * k / R [/itex]
but
[itex]2Ecos(∂) = E[/itex]
so I have
2*Q * k * cos(∂) / R
Now plugging in the values given q = 35.5 x 10^-9 R = .785 m ∂ = 60 degrees k = 8.99x10^9
I get answer 407 N/C but my book is telling me 428. Can anyone explain what I did wrong?
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