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

  • Thread starter Thread starter J-dizzal
  • Start date Start date
  • Tags Tags
    Charge Law
Click For Summary

Homework Help Overview

The problem involves two positively charged spheres with a combined charge and a specified electrostatic force between them. Participants are tasked with finding the charge of the smaller sphere using Coulomb's law.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between the two charges and the implications of their combined charge. There are attempts to set up equations based on Coulomb's law and the combined charge, with some participants questioning the validity of certain assumptions made in their calculations.

Discussion Status

Several participants are actively trying to solve for the charges, with some expressing confusion over previous calculations. There is ongoing dialogue about the equations derived from the problem statement, and some guidance has been offered regarding the setup of these equations.

Contextual Notes

Participants are working under the constraints of the problem's parameters, including the requirement to find the charge of the smaller sphere and the implications of the electrostatic force. There is a noted lack of consensus on the correct approach to solving the equations derived from the problem.

J-dizzal
Messages
394
Reaction score
6

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]
20150907_180049_zpsgysge7lu.jpg
 
Physics news on Phys.org
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!
 
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.]
 
C. Lee said:
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.
 
J-dizzal said:
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
 
J-dizzal said:
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.
 
C. Lee said:
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.
 
Last edited:
C. Lee said:
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.
 
J-dizzal said:
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.
 

Similar threads

Point charge with very thin metal sheet along a spherical surface
  • · Replies 21 ·
Replies
21
Views
2K
Coulomb's law to find electric field for charge density function
  • · Replies 11 ·
Replies
11
Views
2K
Question regarding Coulomb's Law
  • · Replies 8 ·
Replies
8
Views
2K
Force of Repulsion Between Charged Bodies: Calculating with Coulomb's Law
  • · Replies 4 ·
Replies
4
Views
2K
Finding the New Acceleration Given Point Charges
  • · Replies 10 ·
Replies
10
Views
6K
Correct statement about force between two charges
  • · Replies 10 ·
Replies
10
Views
2K
Electric field using Gauss' Law
  • · Replies 3 ·
Replies
3
Views
2K
How do I calculate the force between a charged and a neutral sphere
  • · Replies 5 ·
Replies
5
Views
2K
Finding the Original Charge Given Force
  • · Replies 3 ·
Replies
3
Views
3K
Find charge inner/hollow sphere
  • · Replies 2 ·
Replies
2
Views
2K