On a rainy day, we usually feel the urge to run to avoid getting more wet than necessary. However, the question arises as to whether this strategy would not cause more drops to hit us still, by heading towards them horizontally.
This is a classic debate in Physics , and today we are going to offer you the answer. In the rain, is it better to run or walk? Would increasing the speed of the march cause us to escape the rain or, instead, cause more drops to hit us?
The answer may disappoint you: the amount of rain that falls on you is constant , no matter how fast you go; Although it does matter how long you stay in the rain and how long you travel under it.
To count the water that hits, we have to add the water that falls on you, plus the water that hits frontally as we move. The amount of water that falls on your area of influence is exactly the same, since that area remains constant, regardless of speed and direction. That is, only how long we stay in the rain matters, but not how fast you travel a certain route.
This image created by the Minuto de Física dissemination channel allows a graphic view of this explanation to be obtained.
If we stand still, the area of influence will be smaller, and less rain will fall on us. But if we are moving forward, because we have to go from point A to point B, it doesn’t matter if you move more or less quickly. The amount of water that you are going to pass through is exactly the same.
To better imagine it, let’s make an analogy: every meter you advance would be like hitting a ‘wall of drops’. The more meters you go, the more walls of drops you have to go through. On a journey from point A to point B, the walls of drops that you have to travel are the same, regardless of the speed at which you travel.
But, while the speed of movement does not influence the amount of water that we pass horizontally, the amount of water that falls on us per second does. So, after all, the faster you escape the rain, the less water will hit you.
However, there are other variables to consider. Franco Bocci, a researcher at the University of Brescia (Italy) explained in the European Journal of Physics that both the direction and intensity in which the wind blows as well as the height and physical complexion of the person influence the response.
According to this researcher, in most cases, the general answer is that you have to run as fast as you can. But that solution changes in the event that there are gusts of wind or that the person is quite thin, in which case it is not advisable to run so much. And, if the wind is blowing from behind, the optimal speed will be exactly the same as the wind speed.
Therefore, if you want to get as little wet as possible, it is best to make sure you travel as little distance as possible. And, if you run, watch out for slipping!
