Thursday, April 10, 2014

Center of Gravity Demo

There is a list of center of gravity demonstrations that we do in class to show the concept.  One of them is the famous chair experiment and here it is from "All in the Family."

The same experiment can also be done without a chair and many boys still can't stand up.  But some girls are also unsuccessful with both.

The standard physics explanation is that women can do it but men can't because of the difference in their weight distribution.  Men are supposed to carry more weight in their shoulders and women in their hips so a woman's center of mass is lower and she can lift the chair.

I've never been completely satisfied with that explanation.  We have never taken foot size to height ratios into account.  Nor have we considered the fact that women's shoes tend to hug their feet more than men's shoes.  Leg length to height ratios have never been compared either.  There is no controlling of variables and no rigorous testing.

In other words, are this demonstration and the accompanying explanation good science or not?

2 comments:

  1. Although it's a funny example, I much prefer the "tilted can" example where the full can of soda can't balance on its corner, while a half-full can is able to.

    I guess the good thing about this particular concept is that there are a lot of different practical examples out there that are suitable for in-class demonstration!

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  2. You're right. There are tons of good examples. Sometimes, however, I have explained things in ways that I now question.

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