Thankyou. The force of the 3mC charge from the other two chargers were about .02 difference. Basically one was 9.7*10^(-11) and the other was 9.9*10^(-11). Close to zero as possible, but thankyou.
I subsituted b for 80-a
so using the equation you gave q1= 4mC q2=8mC
4mC*[(80-a)^2] = 8mC*[a^2]
= 4mC* (6400-160a+[a^2]) = 8mC*a^2
which seems more confusing then just doing problem itself
Homework Statement
Two charges are separated as shown. Where would you place a -3 microCoulombs (mC) charge such that the net force on this charge is 0?
+ +
4mC 8mC
Distance between charges are 80cm apart...