Net Electrostatic Force of 4 Charges at a Regular Triangle Pyramid

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Discussion Overview

The discussion revolves around calculating the net electrostatic force on one charge placed at the vertices of a regular triangular pyramid, with a focus on the interactions among the four identical charges. The scope includes theoretical analysis and problem-solving related to electrostatics in three dimensions.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant describes their approach of resolving forces into x- and y-components but indicates that this method did not yield the correct answer.
  • Another participant suggests that the original poster may be misapplying a 2D approach to a 3D problem, emphasizing the importance of considering the geometry of the pyramid and the symmetry of the charges.
  • A participant highlights the need to consider the interior angle that the edge makes with the base plane, which is often overlooked in 3D problems.
  • There is a suggestion that the combined forces on the top vertex should point straight up, indicating a specific direction for the net force.
  • A later reply requests the original poster to share their work to facilitate better assistance, noting that without seeing the calculations, it is difficult to identify potential errors.
  • Another participant acknowledges their mistake in not following forum rules regarding showing work before seeking help.

Areas of Agreement / Disagreement

Participants express differing views on the approach to solving the problem, with some emphasizing the need for a 3D perspective while others focus on the necessity of showing work for effective assistance. No consensus on the correct method or solution has been reached.

Contextual Notes

Limitations include the potential oversight of three-dimensional geometry in force calculations and the lack of specific details in the original poster's attempted solution, which may hinder further discussion.

basanti
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Homework Statement


4 identical charges each equal to Q are placed at the 4 vertices of a regular triangular pyramid of each side equal to 'a'. Find the net electrostatic force on anyone charge.

Homework Equations



F = kQ^2/a^2


The Attempt at a Solution



find the force due to each of the charges, resolve it into x- and y- components and hence add them..but this way i could not get the correct answer.
 
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A problem I used to have is visualizing how the forces would interact. Where I believe you are going wrong is you are trying to make a 3d problem a 2d problem. When dealing with an regular triangular pyramid you'll find that due to symmetry and your charges all being the same most components cancel out.

You should have three forces F1=F2=F3.

You should be using the interior angle, the angle that the edge makes with the base plane. ( most people forget that its a 3d shape and find the angle between the edges.

Hint: If you imagine the pyramid on your desk the combined forces on the top vertex should be pointing straight up out of your desk.

Hope this helps.

Sabastien
 
Last edited:
basanti said:

Homework Statement


4 identical charges each equal to Q are placed at the 4 vertices of a regular triangular pyramid of each side equal to 'a'. Find the net electrostatic force on anyone charge.

Homework Equations



F = kQ^2/a^2

The Attempt at a Solution



find the force due to each of the charges, resolve it into x- and y- components and hence add them..but this way i could not get the correct answer.
Welcome to PF.

Can you show the work you did, so people can see how far you got or where you might have gone wrong? Just saying, basically, "I tried this approach but it didn't work" doesn't really give a good basis for others to provide help. (For all we know, your answer is correct and the "correct" answer is wrong. Or maybe your answer is pretty close to the correct answer, and a reasonable grader would actually give you full credit for your solution. Without seeing your work and your solution, we have no way to tell.)
 
Being new, I responded before reading the rules (which states that you must show your work before anyone can help), my apologies.
 

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