What is the charge on the second sphere?

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The discussion revolves around calculating the charges on two plastic spheres given their repulsive force and distance apart. The first part of the problem has been solved, determining that each sphere has a charge of 7.02X10^-7 C when equal. The second part involves finding the charge on the first sphere when it is four times that of the second, leading to confusion about the calculations. The user eventually clarifies that they need to apply Coulomb's Law with adjusted parameters for a new scenario involving different distances and forces. The problem-solving process emphasizes the importance of correctly applying the formulas to find the unknown charges.
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1. Homework Statement

Two small plastic spheres are given positive electrical charges. When they are a distance of 14.2cm apart, the repulsive force between them has a magnitude of 0.220 N.


A. What is the charge on each sphere if the two charges are equal? Ans: 7.02X10^-7
B. What is the charge on first sphere if it has four times the charge of the other?
C. What is the charge on the second sphere?

2. Homework Equations
Coulomb's Law --> F=kQ1Q2/r^2




3. The Attempt at a Solution

Already solved part A. Having trouble with part b. Both have a charge of 7.02X10^-7 C. The second question says if one sphere is 4 times the other, what is the charge. Wouldn't that just be 4 multiplied by 7.02X10^-7? Thats what I did, and its wrong.
 
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No, that charge is on the spheres if both charges are equal. The distance and force between the spheres is given, and the charges asked if one charge is four times the other one.

ehild
 
Nevermind, got it figured out.
 
Could someone please help me with problem B, except 17cm apart and the Magnitude 0.300N, looking for Q1, Q2. Any help would be e great, I already got problem A answered which is 0.98*10^-6C.
 
If Q2 is four times Q1 then solve the equation

0.3N =k*4Q1*Q1/0.17^2.

ehild
 
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