Posted by Lanise on .
Two 0.09 pith balls are suspended from the same point by threads 40 long. (Pith is a light insulating material once used to make helmets worn in tropical climates.) When the balls are given equal charges, they come to rest 19 cm apart
What is the magnitude of the charge on each ball? (Neglect the mass of the thread.)
q = C

physics 
drwls,
Compute the angle of the strings from vertical. It is sin^1 (8.5/40)
Call this angle A
If the string tension is T
T sin A = F (the Coulomb force)
T cos A = M g
tan A = F/Mg
You need to say what the units of the mass are. All you said was 0.09
The above formula will allow you to compute the Coulomb force F. From that and the separation of the pith balls, you can get the charge