# Electric Charges and Fields

## Homework Statement

two charged spheres 4 cm apart attract each other with a force of 1.2x10^-9 . determin the magnitude of the charge on each if one has twice the charge (of the opposite sign) as the other.

Fe = KQq/r^2

## The Attempt at a Solution

well you are only given Fe and r, plus the info that Q is = to (2)q and k = 9.0x10^9 so im stumped after this step

1.2x10^-9 = (9.0x10^9)(2)qq/16

Last edited:

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kuruman
Homework Helper
Gold Member
In your equation everything is a number except for q. Can you solve it for q? Also, you forgot to convert cm to meters.

could it possibly be that im using the wrong equatiom? and should be using E(force intensity) = kq/r^2 instead of coulombs law??

edit: yes i forgot to convert haha good call..but yea the fact that im finding two charges throws me off...so would just solving for one q give me the charge im looking for, then just double it to get the 2nd charge?

kuruman