Trying to make sense of the strength to weight ratio

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    Ratio Strength Weight
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Discussion Overview

The discussion revolves around understanding the strength-to-weight ratio (StW ratio) in the context of determining whether a table can support a specific weight. Participants explore the application of this ratio to materials and structures, including considerations of design and material properties.

Discussion Character

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

Main Points Raised

  • One participant questions whether the StW ratio can be used to determine if a table can support a 50 kg object, suggesting that the ratio is dependent on the construction of the table.
  • Another participant emphasizes that the StW ratio is typically a material property and may not directly apply to the object being supported, indicating that it is more useful for design purposes rather than load-bearing calculations.
  • Concerns are raised about the different types of strength (compression vs. tension) and how they relate to the design of the table, noting that certain parts may bear more load than others.
  • A participant expresses a desire to find a way to calculate the weight a table can support based on its dimensions and material, indicating confusion over the appropriate terminology and formulas.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the applicability of the strength-to-weight ratio for determining load capacity, with multiple competing views on its relevance and the factors that influence a table's ability to support weight.

Contextual Notes

Limitations include the lack of clarity on specific engineering principles needed for load calculations, the dependence on material properties, and the unresolved nature of how to effectively apply the StW ratio in practical scenarios.

dmehling
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I need some help with something that seems rather simple, but I don't know how to apply the formula. Let's say I have a table and based on the particular material from which it is constructed, it has a strength to weight ratio of 50 kN·m/kg. If I were to place an object on the table that weighed 50 kg, would I be able to use the strength to weight ratio to determine if the table is strong enough to support it?
 
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I do not think so - but I am no expert.

The StW ratio of a table is highly dependent on the construction of the table.

A useful StW ratio will be figured under specific conditions. For example, a beam of dimensions l x w x d made of steel will have a different StW of a comparable beam made of balsa.

You can use that simple calculation to decide - in conjunction with engineering principles - to figure out how to make the table to support a given weight.
 
Is that value for the material or for the table?
Usually it is used as a material (and not object) property. I don't see how will be useful for an object.

Even though is sometimes called strength-to-weight ratio, the usual meaning is that of the ration between the strength (in Pa or N/m2) and density (kg/m3).
So it has nothing to do with the weight supported by an object made from this material.
It is useful when you need to design something as light as possible for a given load or strength.

For your question the strength will be all you need. I mean as material parameter. You need a lot of engineering experience (which I don't have). :)
 
There are several ways to measure "strength". Many materials are stronger in compression than in tension. So knowing how strong something is in tension may not help you design a table that has most of it's parts in compression. The design of the table may also put more load on some parts than others. You have to analyse the forces in each part and ensure each part is strong enough to handle it. Joints can be a weak point as they tend to concentrate forces.
 
I guess I misunderstood the concept. What I am really trying to find out is a way to calculate how much weight an object can support based on its size, thickness, and its constituent material. I have done countless web searches and I can't seem to find the right terminology or formula.
 

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