## Thursday, October 4, 2012

OK...apparently I was wrong.  Someone needs to turn this into a Canadian version of Ocean's 11 pronto.  You can get the full article here.

Aaron Santos is a physicist and author of the books How Many Licks? Or How to Estimate Damn Near Anything and Ballparking: Practical Math for Impractical Sports Questions. Follow him on Twitter at @aarontsantos.

1. Hi,
I am reading your book, 'Ballparking', thank you for writing it. In the chapter, "Honey, I shrunk the Pisarenko", I am not understanding why "the force holding the weight is proportional to the area", why is this so? Is it that I should be thinking pressure rather than just a weight or force. If you could elaborate a little, I would appreciate it. I only have high school physics behind me but I find that scaling relationship quite interesting-the square cube law.
Thanks,
Steve.

1. Hi Steve,

Apologies for the very(!) overdue reply. First off, thanks so much for buying the book! You likely have already figured the Pisarenko problem out, but if not, here's a quick explanation:

We worry about the area because of pressure, which is force per unit area. For example, placing a 10 pound weight on your palm wouldn't be too painful. However, placing a tack between the weight and your palm would be excruciatingly painful even though the weight is still pretty much the same. The reason is because all of the 10 pounds of force gets concentrated in a small area. It's easier for your skin to handle the weight when it's spread out. A similar thing happens with bones and muscle. If your body has a bigger cross-sectional area, then there's more skin and tissue available to push up on the weight. This makes it a bit easier to hold the weight up.

Hope that helps!

Thanks,

-Aaron

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