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Application of Coloumb's Law to electroscope 
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#1
Jun3004, 06:38 PM

P: 258

Hi there, I am having a bit of difficulty with this problem dealing with a little more difficult application of Couloumbs Law.
A large electroscope has two wires that are 75cm long w/22g balls at the ends. When charged, all the charge resides on the balls (Q/2 for each ball) If the wires each make a 30 degree angle with the vertical, what total charge Q must have been applied to the electroscope? So I set up my free body diagrams and I know how to figure out the weight force and i believe i can get tension but what should I be doing to know how much force electrical force is applied (Repulsion in this case since both charges are positive) to make that 30 degree angle to the vertical? I need to be thinking back to mechanics a little bit =P Any help would be appreciated thank you. 


#3
Jul204, 06:26 PM

P: 258

yes net force is = to 0 because a = 0. Thank you I noticed that actually right after i posted this silly me.



#4
Jul1704, 08:23 AM

P: 284

Application of Coloumb's Law to electroscope
Down ward force = mg applied to each side this must be resolved horizontally to equal the charge force which opposes it  a little trigonometry.



#5
Jul1704, 12:14 PM

P: 1,322

There is no horizontal component of a downward force.



#6
Jul1704, 12:59 PM

P: 284

John not directly your right , but the leaves are held apart by a horizontal force and they are trying to fall due to a vertical force , obviously something connects these two.



#7
Jul1704, 02:17 PM

P: 1,322

It isn't the force of gravity, but rather the tension in the leaves, that has the horizontal force component that opposes the charge force.



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