Electric force, tension, charge

AI Thread Summary
The discussion revolves around solving a physics problem involving two charged balls suspended by threads. The user successfully calculated the electric force as 0.00232 N and the tension in the threads as 0.00679 N but struggled with finding the charge on the balls. They initially used the formula q = sqrt[(r^2*Ft*sin 20)/k] but received an incorrect result. Other participants suggested checking calculations and noted a mistake in using electric force instead of tension in the formula. The conversation emphasizes the importance of careful arithmetic in physics problem-solving.
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Homework Statement



Two small plastic balls hang from threads of negligible mass. Each ball has a mass of 0.65 g and a charge of magnitude q. The balls are attracted to each other, and the threads attached to the balls make an angle of 20.0° with the vertical, as shown in the figure below.

http://www.webassign.net/walker/19-36.gif

(a) Find the magnitude of the electric force acting on each ball.

(b) Find the tension in each of the threads.

(c) Find the magnitude of the charge on the balls.


The Attempt at a Solution



I found part (a) 0.00232 N and part (b) 0.00679 N, but I can't seem to figure out part (c)
I used q = sqrt[ (r^2*Ft*sin 20 )/ k ] = 1.93e-8
That answer is not right. Is my formula incorrect? Please help
 
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I think the equation looks right. I got a completely different answer using it though. I suspect you have made an arithmetic error. Check your calculations.
 
Last edited:
I was using the electric force instead of the tension! Silly mistake. Thank you
 

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