Coulombs's law problem, asked to find an unknown charge.

[J-dizzal]

Homework Statement

Two small, positively charged spheres have a combined charge of 23.0 × 10-5 C. If each sphere is repelled from the other by an electrostatic force of 0.800 N when the spheres are 2.00 m apart, what is the charge on the sphere with the smaller charge?

Homework Equations

Coulomb's law F=k q₁q₂/r²

The Attempt at a Solution

im very stuck on this one.[/B]

 

[C. Lee]

You do not need to keep indicating they are absolute values since it is clarified in the problem that they are positively charged.

Since you have two equations about q1 and q2, you can now solve them easily!

 

[TSny]

You have a good start. Now try to use the fact that the two charges have a combined charge of 23.0 x 10^-5C.
[EDIT: Sorry, C. Lee. You posted while I was still typing my post.]

 

[J-dizzal]

You do not need to keep indicating they are absolute values since it is clarified in the problem that they are positively charged.

Since you have two equations about q1 and q2, you can now solve them easily!

I tried to solve for q₁ and q₂, and i got q₁=0 and q₂=23E-5. my answers are true but not the correct solution to this problem.

 

[SteamKing]

I tried to solve for q₁ and q₂, and i got q₁=0 and q₂=23E-5. my answers are true but not the correct solution to this problem.

How did you come up with these figures? If q₁ = 0, then the force = 0, since the product of the charges = 0.

You'll have to post your work

 

[C. Lee]

I tried to solve for q₁ and q₂, and i got q₁=0 and q₂=23E-5. my answers are true but not the correct solution to this problem.

I don't get how you ended up there. If q1 = 0, q1*q2 cannot have nonzero value.

 

[J-dizzal]

I don't get how you ended up there. If q1 = 0, q1*q2 cannot have nonzero value.

I'll try again to solve, this are my 2 equations: q₁+q₂=2.3E-4 and q₁q₂=3.5605E-10.

 

[J-dizzal]

I don't get how you ended up there. If q1 = 0, q1*q2 cannot have nonzero value.

im having trouble solving this. this is my first step from the starting equations; q₁+(3.5605E-10/q₁)=2.3E-4. and then i factor out q₁ from the left side of the equation and solve from there.

 

[C. Lee]

im having trouble solving this. this is my first step from the starting equations; q₁+(3.5605E-10/q₁)=2.3E-4. and then i factor out q₁ from the left side of the equation and solve from there.

Now you have quadratic equation there, q₁²+3.56E-10 = 2.3E-4*q₁, which you can easily solve.