It’s official, banana skins are dangerous

Banana PeelI love the IgNobel prizes, they’re great. Their stated aim is to make you laugh and to think, and what is better than having a laugh and thinking about something new? This year’s winners were excellent as usual. I particularly liked the 2014 Physics IgNobel.

This rewarded a long overdue piece of research. The mighty Wikipedia reckons that we have been laughing at the slipping-on-a-banana-skin gag since the 1920s. But it was only in 2012 that Mabuchi and coworkers actually measured the coefficient of friction of a banana skin on a (linoleum) floor, to see if they are indeed slippery. And the answer is that indeed they are slippery, the coefficient of friction is only around 0.07. In other words for every Newton of downward force there is less than a tenth of a Newton of friction. As Mabuchi et al. point out, this is only a little higher than that of a ski on snow. For say a rubber sole on tarmac the coefficient of friction is about ten times higher, so by stepping on a banana skin you are reducing the amount of grip you have by about a factor of ten, enough to cause you to slip.

In science, speculation is cheap but data is king. For decades people have assumed banana skins were slippery but have not quantitatively measured this. Mabuchi and coworkers have done the world’s slapstick comedians a favour and proved that like most good comedy their gag is based on truth.

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