Walking or Running in the rain?

You are going home after spending some time in the library and suddenly it begins to rain. The closest shed from where you are is some good metres away. In this case you are left with two options; it is either you run to the shed or walk quickly to the place. The question now is, to avoid excess wetting of your clothes which would be more beneficial?

Yes! I know common sense (which is not common to some people) would tell you that it is better to run than to walk. But what's the reason to that?

Some scientists have tried to analyse this notion by carrying out experiments to know the best method of avoiding excess wetness. Some concluded that walking exposes less part of the body to the rain while running exposes (to a great deal) the anterior of your body thereby causing the individual to get wet excessively. Well this observation is true bearing in mind that there is an angle between the rainfall and the person involved (sometimes you feel the rain coming from the front, sometimes from the back and most times it just comes straight down. This is due to the action of wind). But walking in the rain makes you spend more time in the rain giving it more time to hit you.

Running, however, is a faster mode of movement to walking. And Nick Allen, a British inventor was able to deduce a formula to explain this concept and I’ll try to break it down so that we can all understand.

assuming W= total wetness i.e. the total mass of rainwater on your body.

p= the density of rainwater

a= top surface area of the body (that big head of yours...lol)

A= front surface area of the body( the chest downward)

V_R= velocity of the rain

V_P= velocity of the person

t= time spent in the rain.

From these parameters he got;

W=P(aV_R + AV_P)t

Looking at the equation clearly, the only quantities we can directly control are ‘t’ (the time spent in the rain) and V_P (how fast we can move).

The equation shows to us that we get very wet if we stay out in the rain for a long time i.e if we are walking or running without a destination. Surely running towards shelter would minimize the time spent in the rain. And so, if the distance to the shelter is D, then the time spent in the rain (‘t’ in the equation) will be D/V_P and if we insert this into the "total wetness equation" to replace t, we get W=P[aV_R /VP+A]D

So, we can see that maximizing our velocity is a good idea to stay less wet. Therefore the next time it starts to rain, first identify the nearest shelter, and the run to it as quickly as you can.