Apr 20 2011

Why Is It So? – Should you run or walk in the rain

If you’re caught in the rain without an umbrella, will you get less wet if you run or walk?

I remember Grunter, Luke and I having this discussion at school. Luke came up with a thought experiment – if you could run at infinitesimal speed, you would not get wet on the head but would catch all the rain drops between you and your destination on the front of your body. If you walked very very slowly, you would get drenched on the head.

This is the approach used by Prof Lewin at MIT in the (very long) mathematical explanation below. (what is it with these TV professors – he looks just like Prof Julius Sumner Miller). His conclusion was similar to Luke’s – run as fast as you can, leaning forward at as much of an angle as you can to minimize your collisions with rain drops ahead of you.

The Mythbusters team had two cracks at answering this question – rather than rely on physics, they walked and ran in the rain and then compared the increase in weight of the clothes they were wearing to estimate how wet they got.
The first result in 2003
http://dsc.discovery.com/videos/mythbusters-running-in-the-rain-minimyth.html
And their second go

Their conclusion after the second experiment concurred with Prof Lewin – run.

All this trouble could have been saved if everyone had remembered this old adage.

When caught in the rain without mac,
Walk at the pace of the wind at your back,
If the wind’s in your face,
Then the ideal pace,
Is as fast as your legs can make track.