Point Charge Problem: Net Force Calculation

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Homework Help Overview

The problem involves calculating the net force on a point charge due to two other point charges, all of which are positive. The charges are positioned in a two-dimensional coordinate system, and the original poster attempts to apply Coulomb's law to find both the magnitude and direction of the net force acting on one of the charges.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of Coulomb's law and the use of vector components to determine the net force. There are questions regarding the signs of the force components and the interpretation of the angles involved in the calculations.

Discussion Status

Some participants have provided guidance on the vector nature of forces and the importance of consistent sign conventions. There is ongoing exploration of the calculations, particularly concerning the angle determination and the implications of the charges being the same.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. There is a noted confusion regarding the effects of similar charges and the resultant vector calculations.

azila
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Homework Statement


Two Positive charges q1 = q2= 2.0 microC are located at x=0, y = .30 m and x =0, y =-.30m. Third point charge Q =4.0 microC is located at x=.40 m, y = 0. What is the net force magnitude and the direction on charge q1 exerted by the other two charges.


Homework Equations


coulomb's law


The Attempt at a Solution



Ok, so this is what I did. I drew the charges and then for the point charge Q acting on q1, i drew out the components and everything. So, first I just solved for the F(Q on q1)=k(Qq1)/(.50^2). I found the .50 through the pythagorean theorem. So I get .29 N. Then for the components. I solved that by having the x component be negative since cos is negative in the second quadrant and y component is positive since sin is positive in the second quadrant. I got the respective values to be -.17 and .23. Then I did F(q2 on q1). There is no x component and there is only a y component. The y component through coulomb's law, comes out to -.1 since they both are positive and so they repel. So, the Fx is -.17 and Fy is .23-.1 which is .13 N. I found the resultant to be .21 and theta to be 37 degrees. However, this is not the right answer. Any thing that I am doing wrong??Or am i not even following the steps correctly..I would appreciate any help. Thanks..
 
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azila said:

Homework Statement


Two Positive charges q1 = q2= 2.0 microC are located at x=0, y = .30 m and x =0, y =-.30m. Third point charge Q =4.0 microC is located at x=.40 m, y = 0. What is the net force magnitude and the direction on charge q1 exerted by the other two charges.


Homework Equations


coulomb's law


The Attempt at a Solution



Ok, so this is what I did. I drew the charges and then for the point charge Q acting on q1, i drew out the components and everything. So, first I just solved for the F(Q on q1)=k(Qq1)/(.50^2). I found the .50 through the pythagorean theorem. So I get .29 N. Then for the components. I solved that by having the x component be negative since cos is negative in the second quadrant and y component is positive since sin is positive in the second quadrant. I got the respective values to be -.17 and .23. Then I did F(q2 on q1). There is no x component and there is only a y component. The y component through coulomb's law, comes out to -.1 since they both are positive and so they repel. So, the Fx is -.17 and Fy is .23-.1 which is .13 N. I found the resultant to be .21 and theta to be 37 degrees. However, this is not the right answer. Any thing that I am doing wrong??Or am i not even following the steps correctly..I would appreciate any help. Thanks..

Force is a vector. If you take it that a force in the positive y direction is positive (as you have done so when finding F(Q on q1), then the F(q2 on q1) is also positive, as it exists in the direction of the positive y axis...
 
oh so it doesn't matter that they have the same charges... is that right?
 
ok, i got the magnitude but the angle is not working. I get 63 and then i subtracted from 90 to get Counterclockwise, to be 27 but it does not work..
 

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