Can toothpicks and wood glue mimic real bridge designs for a school project?

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Discussion Overview

The discussion revolves around the feasibility of using toothpicks and wood glue to construct a bridge model for a school project, specifically whether real bridge designs can be applied to this scenario. Participants explore the implications of different shapes and forces acting on the bridge, considering concepts from physics and calculus.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether designs for real bridges can be adapted for a model using toothpicks and wood glue, particularly focusing on the application of force at the center of the structure.
  • Another participant suggests that real bridge designs would indeed work, proposing that an arch might be optimal, while also considering an inverted V shape.
  • A different viewpoint indicates that the optimal shape depends on how the force is applied, suggesting a pyramid shape for point forces and an arch for distributed forces.
  • One participant expresses agreement with the idea that the orientation of the V shape (upright or inverted) does not significantly impact its effectiveness.
  • The original poster clarifies that the project does not require a road deck and mentions the instructor's method of adding weights to test the structure's strength, expressing interest in researching curves for a report.

Areas of Agreement / Disagreement

Participants generally agree that real bridge designs can be applied to the toothpick model, but there are multiple competing views regarding the optimal shape based on the type of force applied. The discussion remains unresolved regarding the best design choice.

Contextual Notes

Participants reference concepts such as bending moment diagrams, catenaries, and parabolas, but there are limitations in the discussion regarding the specific assumptions about force application and the lack of detailed mathematical analysis.

Who May Find This Useful

This discussion may be useful for students or educators interested in bridge design principles, model construction techniques, and the application of physics in engineering projects.

technoweasel
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I have a question about bridges. I am not sure if this is the right place, since everyone else is discussing more advanced things, but I couldn't find anything (I did try to search). If this post is out of place just please redirect me.

For school I need to design and then build a bridge to connect 2 supports that are about a foot apart, using only toothpicks and wood glue. My question is this: Would designs for real bridges work in this situation, even though the force will only be applied to a point in the center of the structure? I have read a bit about the parabola and catenary in calculus books, but would a curve be best in this situation? If a cable supporting a uniform weight (along the x axis) makes a parabola, and it can be inverted to create an arch with the forces reversed, then can a cable supporting a single weight that pulls it down in a V shape be reversed to make an optimal arch for this application?

What is wrong with my reasoning? I haven't been through physics in school yet, so I might not even be asking the right questions. Please help me by explaining what is going on or redirecting me to some good online resource.
 
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Yes, real bridges would work in this situation. An arch would perhaps be optimal, but an inverted V would work well, also. Your reasoning sounds correct.
 
The ''best'' curve depends on that how force is applied to the bridge. The bridge form should mirror bending moment diagram. For point force in middle it would be shape of a pyramid, for distributed force it is an arch.
 
Makes sense. I currently agree with the post by archis now, which matches the concept posted by technoweasel. And by the way, technoweasel, it doesn't really matter if the V is upright (below the bridge) or inverted.
 
You're right, nvn.

Thanks, guys. If I wasn't clear, the "bridges" do not require a road deck, and the instructor adds weights to an area near the center of the span until the structure collapses. Are there any web pages that discuss this in detail? I might use a curve anyway because I have to do a report and it would be much more interesting to write about curves and their derivation. However, I guess I could write about the caterary and parabola and why I decided NOT to use them. I will continue researching.
 

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