Calculate scaled down human model weight for practical experiment

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Discussion Overview

The discussion revolves around calculating the weight of a scaled-down human model at a 1:20 ratio, specifically for a model that is 9 cm tall. Participants explore various methods and considerations for determining the weight, including density, BMI, and scaling laws.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests using the average density of a human to calculate the weight, questioning what that average density is.
  • Another proposes using the BMI formula to determine weight based on a chosen BMI and the scaled height.
  • Some participants argue that weight scales with volume, indicating a reduction by a factor of 8000 for the 9 cm model.
  • Concerns are raised about the implications of scaling down structures, noting that smaller models may require different considerations for material strength.
  • A participant introduces a more complex argument about weight scaling with the fourth power of the scale, referencing gravitational effects and density assumptions.
  • There is a discussion about the relevance of the term "weight" versus "mass" in the context of the OP's inquiry.
  • Viky mentions an average human density of 1 kg/m³, leading to a calculated weight of 4 kg for the scaled model, which is met with skepticism by others.
  • Another participant points out that the BMI formula traditionally assumes a square relationship with height, while empirical evidence suggests a 2.5 exponent may be more appropriate.

Areas of Agreement / Disagreement

Participants express multiple competing views on how to approach the calculation of the model's weight, with no consensus reached on the best method or the implications of scaling. Some agree on the basic principles of scaling, while others challenge the assumptions and calculations presented.

Contextual Notes

There are unresolved questions regarding the assumptions made about density and the implications of scaling laws, particularly in relation to structural integrity and gravitational effects. The discussion reflects a variety of approaches without a clear resolution.

Who May Find This Useful

This discussion may be of interest to those involved in experimental design, model scaling, or anyone exploring the implications of physical laws in scaled-down scenarios.

  • #31
Viky1147 said:
And by guidance means, i meant if you couldn't answer you could direct me towards the answer is what i meant.
I have counted several simple answers in this thread - including one from me. There are also the reasonings behind them. Your 'figurine' could be made of any material that's just a bit less dense than water and you could test this by checking it floats with only a small proportion above water.

It seems that you have ignored the questions that we have asked but many of them could be very relevant if you plan to do anything more than just stand this figure on your 'apparatus'. Did you consider re-stating your question to make it clearer what you really mean? It appears that you want to keep this project a secret and so the information you have taken from the thread may let you down.
 
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  • #32
Viky1147 said:
Now don't say data is insufficient. This is what the requirement is.
The data is insufficient. We need to know what particular aspect you are attempting to model.

If you were trying to model pressure on shoe material then scaling the weight down by a factor of 202 = 400 could be appropriate. That would preserve the pressure per square inch on the shoe material.
 
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  • #33
jbriggs444 said:
The data is insufficient. We need to know what particular aspect you are attempting to model.

If you were trying to model pressure on shoe material then scaling the weight down by a factor of 202 = 400 could be appropriate. That would preserve the pressure per square inch on the shoe material.
My question is this
I need to Scale down a human model (height & weight) for a study.
I couldn't experiment it on a 1:1 model, due to cost.
So, I need a human model of 9cm height.

What data is missing here in your proposed calculation?
 
  • #34
Viky1147 said:
My question is this
I need to Scale down a human model (height & weight) for a study.
I couldn't experiment it on a 1:1 model, due to cost.
So, I need a human model of 9cm height.

What data is missing here in your proposed calculation?
The purpose and methods of the study. If you want the scale model to behave similarly to an unscaled human, those details matter.
 
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  • #35
Thread closed temporarily for Moderation...
 
  • #36
We seem to be stuck on the spot and reasoning becomes ad hominem from the OP's side.

I further suppose that there is no answer to the question, especially since ...
jbriggs444 said:
The purpose and methods of the study. If you want the scale model to behave similarly to an unscaled human, those details matter.
... remains unanswered.

This is the standard trick for arguments: missing details followed by ad hominem responses demanding to leave the discussion. However, it is not the way we debate questions on PF.

Thread remains closed.
 
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