How is force distributed orthogonally along a material plane?

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Discussion Overview

The discussion revolves around the mechanics of a thin rectangular board supported by two springs, focusing on how force is distributed orthogonally along the material plane when pressure is applied at various points. Participants explore the implications of this setup on the forces acting on the springs and the equations governing the motion of the system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions how the force acts on the springs when pressure is applied at different points on the board, noting that pressing directly above one spring compresses only that spring.
  • Another participant suggests using moments about the other spring to determine the force on each spring.
  • A participant expresses difficulty in formulating the motion equations for angular momentum and considers the possibility of numerical solutions due to the complexity of the system.
  • The same participant seeks clarification on the result of performing two infinitesimal rotations around different points in 2D space.

Areas of Agreement / Disagreement

The discussion reflects uncertainty regarding the distribution of forces on the springs and the complexity of solving the motion equations. There is no consensus on the best approach to analyze the system or the outcomes of the proposed methods.

Contextual Notes

Participants mention the potential unsolvability of the differential equations analytically, indicating limitations in their current approach. The discussion also highlights the need for clarity on the mechanics of rotation in the context of the setup.

pL1
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Hello,

I want to simulate a plane thin rectangular board attached to one spring below at each end. (So there are 2 springs in total.) The springs span the entire edges. The spring-board-attachment is a rotatable axis.

I can't find out how the force acts on the springs. I don't know whether there will be any force on the spring below at the farer end. If I press directly above one end onto a spring only this spring gets compressed while the other does not because the board only rotates around its axis? If I press onto the center of the board, both springs receive equal force. What is with any other point of pressure though? What's the downwards force onto the springs??

Thanks!

pl1
 
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Welcome to PF!

Hello pL1! Welcome to PF! :smile:
pL1 said:
What is with any other point of pressure though? What's the downwards force onto the springs??

To find the force on each spring, take moments about the other spring. :wink:
 
This sounds good!

Thank you!

And thank you for the welcome!

pL1
 
Hello,

I was actually unable to write down the motion equations for the angular momentum. However I have derusted myself a bit and wrote down the Euler-Lagrange DE system.
Now I don't seem able to solve it. It may even be unsolvable as the setup incorporates a gravitational pendulum of sorts for which the DE can't be solved analytically.

This is why I am thinking of solving it numerically. Now I obviously have to do 2 (infinitesimal) rotations around 2 different rotation points in 2D space in one iteration. But the question is: what's the result of 2 such rotations: vector addition of each start-/end-rotation connection vector? I can't make up my mind.

http://www.alice-dsl.net/l.hansen/spring_board_Euler_Lagrange_DE.PNG

Thus thanks for any help!

pL1
 
Last edited by a moderator:

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