Why is an empty shampoo bottle so easy to knock over?

Originally published at: https://boingboing.net/2020/04/27/why-is-an-empty-shampoo-bottle.html

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The reason: empty bottles have much less mass than full bottles, and their center of gravity is higher so they are basically begging to fall over at the slightest touch.

Well, DUH!

Barely even worth an Ignobel Prize.


I’m a little surprised that I didn’t have to click through 10 pages to find out. The best way to find out the answer to one of these clickbait questions is to google it - clicking on the link is an exercise in futility.


I do believe that bottle is meant to be stored lid-down so that the center of mass always stays below the centerline.


A shampoo bottle with a rounded cap is one of the most obvious design flaws I can’t believe is still widely implemented.


The vast majority of things are designed to be sold, not used.


I dare this guy to knock a battery off Robert Conrad’s shoulder. Then we’ll see how tough he is


Pah. I’ll bet the Duracell Bunny could take him down just like that.




Read headline.
Thought for 4.5 seconds, imagined answer.
Read “article.”
Found I was correct.
My next 4.5 seconds spent determining that Universities waste f*cktons of money.
Surmise: most Boingers share such powers of intellect.

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Teaching physics has to be teaching intro physics at some point.


Hang on…hang…one second (checks notes) it’s because…The taller they are the harder they fall.


That’s what I thought at first, but the second test in the video demonstrating a nearly 10-fold increase to impact responsivity was a genuinely interesting finding (Hypothesis: Many assumed they knew where the instructor was going and didn’t actually watch the whole video? :wink: )

It’s the change in center of gravity coupled with the massive reduction in mass that causes them to be so danged annoying. Obvious, of course, but not quite as simple as I initially assumed.


One and all.

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Next Up. Why Weebles Wabble But They Don’t Fall Down.

We need more hard hitting science journalism like this.


I think you meant Pulitzer Prize right? The Noble Prizes are for journalists what do well in science. I’m probably the most, the person with the most knowing, i know the most about these things.


I watched the video. I’m afraid it’s still: duh!

The reduction in mass as it empties is the biggest “bleedin’ obvious” thing. The change in the centre of gravity is almost as obvious but not quite. It needs a few seconds thought (no experimentation) to realise the extra plastic gubbins in the lid will at some point start to outweigh the increasingly small mass in the bottle as it tends towards empty.

So, double-duh!

But I grant that
(a) He did say the physics of it was easy to understand. And he did find some numbers via experimentation, that may be useful. His method may have a practical application for bottle designers to review the design elements of base shape and area vs. height and extra mass of plastic gubbins in the lid parts, to minimise tippability as a bottle empties. If they cared. That some design their labels to read the other way up indicating that the bottle is intended to be stood on its ‘lid’ suggests some do care.
(b) The BoingBoing headline (“Why…”) is a perhaps more to blame for such a strong ‘duh!’ reaction than anything actually said in the video.

Nevertheless, still double-duh. :wink:

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Thanks, this definitely counts as a Wonderful Thing to me!

This could be fixed by making the bottle walls an inch thick, leaving a small tube for shampoo in the middle. As most of the weight of the product is now the bottle, emptying the shampoo should have little effect on its stability. A bonus side effect for retailers is now many more bottles much be purchased to get the same amount of shampoo, therefore increasing profits.

The bottle will have to be redesigned a bit with some sort of plunger, as it will be impossible to squeeze out the product out of such a thick bottle. Please visit my Patreon to donate to this important effort.

But would you have expected a 10-fold decrease in stability?

Regardless, I’ll have to concede that you have superior deductive reasoning skills relative to my own. I would have stopped at center of mass, and would have assumed I’d figured it out.

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