Electric force, tension, charge

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SUMMARY

The discussion centers on calculating the electric force, tension, and charge of two small plastic balls with a mass of 0.65 g and an angle of 20.0° with the vertical. The electric force acting on each ball was determined to be 0.00232 N, while the tension in the threads was calculated as 0.00679 N. The user attempted to find the charge using the formula q = sqrt[(r^2 * Ft * sin 20) / k], but initially arrived at an incorrect value of 1.93e-8 due to using the electric force instead of the tension in their calculations.

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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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