A Daily news digest by Jasper van Santen

Staying dry in rain depends on body size – Telegraph

In Nonsense on July 24, 2012 at 20:53

Staying dry in rain depends on body size

While the natural response to a downpour may be to find shelter as quickly as possible, scientists have long argued that the situation is far more complicated than it appears.Some have suggested that running or walking made little difference to your overall exposure to raindrops, but others have argued that an optimal speed may exist depending on the direction and strength of the wind.Now an Italian physicist has complicated the problem further by arguing that the answer depends on another, previously unexplored factor: the body shape of the person in question.Writing in the European Journal of Physics, Prof Franco Bocci explained that while running through a shower will get you to shelter quicker, walking may mean less rain falls on your front at any one time.In calm conditions when rain falls directly downwards, or when there is a head wind blowing the rain towards you, Prof Bocci found that the most sensible solution would generally be to seek cover as quickly as possible.

When the rain blows in from behind, the best answer in theory would be to match your pace to the exact speed of the wind, meaning both your front and back would stay largely dry. But in certain weather conditions the optimum strategy for staying dry becomes more complex, depending on factors including raindrop size and even a persons body shape, Prof Bocci added.When the wind comes in from the side, he explained, thinner people are exposed to much less of the rain than larger people with a more rounded figure.In such cases the fatter person should run as fast as they can to escape the rain while a thinner person who presents a smaller target would still be better matching their speed to the wind, he said.Prof Bocci summarised his findings by telling the BBC: “Lets say that in general, the best thing is to run, as fast as you can – not always, but in general.”If youre really thin, its more probable that there will be an optimal speed. Otherwise, its better to run fast.”Prof David Tong, a Cambridge physicist who was not involved in the research, said: “Its surprisingly complicated, actually. The new factor that comes in is when you have some wind, so the rain is coming in and falling at an angle. Now it actually depends on the shape and size of your body as to what you have to decide to do.”Asked about the significance of the paper, he added: “Its not exactly the Higgs boson – I think its just a fun bit of mathematics that a few people have been playing with.”


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