Charge on pith ball between two plates

AI Thread Summary
To determine the charge on a pith ball suspended between two plates, the mass is given as 40 milligrams, the potential difference is 480 V, and the plate separation is 6 centimeters. The ball hangs at a 20-degree angle to the vertical, indicating a balance of forces. The relevant equations include F=ma, E=F/q, and V=E/d, which are crucial for calculating the electric field and resulting charge. The expected answer is 1.8x10^-8 C, but the poster is unsure of their calculations and seeks clarification on their approach. Additionally, there is a correction regarding the unit conversion from grams to milligrams.
fizzicmaniac
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Homework Statement



The mass of the ball is 40 milligrams, the applied potential difference is 480 V and the plate separation is 6 centimeters. If the string hangs at an angle of 20 degrees to the vertical, determine the charge on the pith ball.

Homework Equations


[/B]
F=ma
E=F/q
V=E/d

The Attempt at a Solution



This is my work shown to the end, although the answer is wrong I'm not sure what I missed, and any help would be greatly appreciated. The answer is supposed to be 1.8x10^-8, but I'm not sure how to get there.
http://imgur.com/a/sgRUX
eiUz7DD.png
 
Last edited by a moderator:
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fizzicmaniac said:
V=E/d
Really?
 
Also:
fizzicmaniac said:
The mass of the ball is 40 milligrams

upload_2016-12-17_6-6-53.png


Grams are not milligrams!
 
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