How Slippery the Banana Skin is?

How to make a fool of yourself with a banana skin – Day 228 of Project 365 by Matthew on https://flic.kr/p/6bQRWP licensed by Creative Commons

Banana Skin? The One We saw in the Cartoon?

It must be a very familiar scene that a yellow octopus-like object is on the road and a cartoon character runs onto it then falls and rolls over the street or even runs into a shop. Yes, we all saw that on TV or when we play video game such as Mario GoKart! while we were children.  Do you ever wonder why and how it go? Or do you ever step on a banana skin and hit your face or back on the ground? Well, I never have that experience and definitely I don’t want to. However, I guess the researcher from the School of Allied Health Sciences and Graduate School of Medical Sciences of Kitasato University in Japan must have terrible experience on the notorious joke. Otherwise, they won’t publish the Frictional Coefficient under Banana Skin on Japanese Society of Tribologists and win the Ig nobel prize for physics in 2014.

How They did It?

Based on the method in that paper, they used set a sensor which can detect normal and lateral force at the same time and then put a banana skin, giant cavendish species and set as yellow skin on the top, on it. An unfortunate poor guy then stepped on it and fall like a shit, ok there was no shit,  then they could measure and calculate the frictional coefficient as 0.07 by the equation u=(Fx^2 +Fy^2)^0.5/ Fz. They also tested skins from other fruit such as apple, lemon, orange and even tried the dried banana skin or reverse side, yellow side at the bottom, and the conclusion proved that the normal image of yellow at top is the most frictionless trick to have people fall on the ground. Well, seriously, how slippery it is ? The banana skin may lose in the competition to ski on the ice but it could win that of two polished metal surface even with grease in between. They even cited that other journal suggested that more than 90% possibilities that a normal human would tumble while he stepped on the surface with a friction coefficient smaller than 0.1. Remember, banana skin is 0.07!

Seriously, It’s Science!

Yes, seriously speaking, it is a scientific research. The above discussion would make this look like a scientific exhibition topic in high school. In fact they did much more to discover that actually a composition called polysaccharide follicular gel was found to be rich in the white side of the banana skin and when the skin was pressed, the polysaccharide follicular gel would flew in between the surface and formed a very homogeneous layer and worked as a very good lubricant then we tumbled!

I have to admit that sometimes Japanese would be too serious about everything and this research would be one example of that. However, think about the possible usage of lubricant, recovery or reuse of the biowaste, or just the scientific spirit in the research. I really wish much more application depend on this would be developed. At least, the following words may help you to citing, searching, and reading rate of this paper: Ig nobel prize, Japan, and Tribology. (with evil smile T_T)

4 Responses to “How Slippery the Banana Skin is?”

1. zengd says:

The polysaccharide follicular gel is found not rich in the other fruit skin and therefore the researchers believe that the banana skin is so slippery mainly due to it. 🙂

2. vchhen says:

Nice post zengd! Do you know if this polysaccharide follicular gel would be found in the skin of other fruits granted that apples, oranges and lemons are out of the picture?

3. zengd says:

Well, actually they do that! They have not only studied the other fruit skin but also the dried banana skin. You can read it from the paper they published. And definitely the more fresh the polysaachiride gel works better.

….Sometimes you have to say that Japanese researchers are too serious and focus on the details too much!

4. Abe says:

So interesting to hear that there have actually been studies on this sort of thing! Turns out there was more truth in all those cartoons than i ever would have thought!

It would be interesting to see how this friction coefficient increases with time as the banana skin dries out..