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Finding theta for Coloumb's law suspension

  • #1

Homework Statement


Two spheres are suspended on strings and repel each other. Using the graphing function of your calculator setup and solve a formula to find theta.

The length of the rope is 3.0m, q = 1.0e4 and m = .2 kg.

Homework Equations


F=k*q1*q2/r^2

The Attempt at a Solution


Using newton's second law I've tried several times to set up the formula to solve for theta but I am unable.

I know that the y component of tensions is equal to the force of gravity. Also that the X component of tension is equal to force caused by the repulsion of the two charges.
 

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Answers and Replies

  • #2
BvU
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Equations look OK to me. Perhaps the instruction means they want you to solve numerically, not analytically ?
 
  • #3
We were told to find the equation, set it equal to zero and plug in our given mass, charge and length then find the x intercept with a graphing calucator. I get 60 degrees which is about twice what it should be.
 
  • #4
BvU
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Can't find any givens under

Homework Statement


[/B]​
Perhaps you can use this thread to check if your calculator works properly

(Although I admit that for the numbers at the bottom of your sheet ##\pi/3## fits a lot better than ##\pi/6## :) )
 
  • #5
Oops, that's what I get for being in a rush. The length of the rope is 3.0m, q = 1.0e4 and m = .2 kg.
 
  • #6
BvU
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Hefty charge !
 
  • #7
Oh jeeze I just cannot type tonight. q = 1.0e-4
 
  • #8
BvU
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Well, as I said,
for the numbers at the bottom of your sheet ##\pi/3## fits a lot better than ##\pi/6## :)
So I'm at a loss. How do you know that it's not right ?

(can always try the check with this other thread to see if that fits...)
 
  • #9
My professor said that the angle should be about 30 degrees. It's possible I misheard though. I can't find an error so I think that might be the case.
 

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