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I thought I did this correctly and my answer turned out incorrect. Here's the problem:

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This is what I did:

In order to use Coloumb's Law, I need r, the distance between the two charges.

[tex]\arcsin{4}=\frac{x}{0.24m}[/tex]

[tex]x=0.24\arcsin{4}=0.098m[/tex]

[tex]r=2x=0.196m[/tex]

So that's r.

Then I need to pick one side of this thing apart and break it down into x and y-components.

With the weight, I have three forces acting on this thing. The tension in the rope, the weight, and the electrical force repelling each sphere.

My goal is to find the x-component of the electrical force so I can then plug it into Coulomb's law and find the charge.

For the weight,

Wx=0

Wy=-mg=-0.98

For the tension,

Tx=-Tsin4

Ty=Tcos4

For the electrical force,

Fx=Tsin4

Fy=0

To find T, all I did was:

FyNET=Wy+Ty+Fy=Tcos4-mg

(net force of y-component)

T=mg/cos4

Right??

So for T, I get 0.098239

Plugging that into Tx, I get 0.006853

And then it goes into Coulomb's law. Which I have reformatted this way:

[tex]F=\frac{kq^2}{r^2}[/tex]

...Because both charges are supposed to be equal...

Moving that around, I get:

[tex]q=\sqrt{\frac{Fr^2}{k}}[/tex]

Plugging in values, I got 1.711e-7

What did I do wrong?

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# Homework Help: Tension And Electric Charge

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