Point charges and force of repulsion

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Homework Help Overview

The discussion revolves around the forces of repulsion between two point charges, specifically examining how the force changes when the distance between the charges is altered. The subject area is electrostatics, focusing on Coulomb's law.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to identify the relevant equation for calculating the force of repulsion and expresses uncertainty about how to proceed. Other participants inquire about the scaling of the force with respect to distance and discuss the implications of reducing the distance between the charges.

Discussion Status

Participants are exploring the relationship defined by Coulomb's law and questioning the effects of changing the distance on the force of repulsion. Some guidance has been offered regarding the scaling behavior of the force as the distance decreases, but there is no explicit consensus on the final interpretation or calculations.

Contextual Notes

There is some confusion regarding the application of the equations and the interpretation of the results, particularly concerning the use of a negative sign and the scaling factor when the distance is reduced.

kbyws37
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Two point charges are separated by a distance r and repel each other with a force F. If their separation is reduced to 0.280 times the original value, what is the magnitude of the force of repulsion between them?


I don't really understand this question and don't know where to start.
Would I start with the equation
E = ((k)(Q)/r^2

what follows next?
 
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What is the equation for the repulsive force between two point charges, and how does it scale with r?
 
JeffKoch said:
What is the equation for the repulsive force between two point charges, and how does it scale with r?

It would be Coulomb's law of

F = ((k)(q1)(q2))/(r^2)

So it would be -0.280 times the original r value?

The final answer is 12.8 F but I still don't understand.
 
Where do you get the minus sign?

O.K., you know that F scales as 1/r^2. When r gets smaller, F must get larger. When r is half it's original value, how much larger does F get?
 

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