High School Is It Better to Run or Walk in the Rain?

[jbriggs444]

Just pretend that you do not care whether it is raining. If you pretend anything long enough and well enough, it ceases to be a pretense.

 

[Hornbein]

One can see right away that wetness will be roughly inversely proportional to speed of the walker. 1/s. This decreases rapidly with increases in s. The incidence of rain on the side of the walker increases with the sine of the arc tangent of s/r, with r the speed of vertically falling drops. This increases rapidly but not nearly as fast as 1/s decreases. So moving as fast as one can wins.

 

[jbriggs444]

I like modelling the body as a right rectangular prism (a cuboid). In the absence of wind, the rain will only ever strike the front and top faces. The front face sweeps out a fixed amount of rain regardless of walking speed. The top face is rained on at a constant rate regardless of walking speed. The best strategy is to walk fast so that less time is spent getting the top wet.

No calculations involved.

 

[A.T.]

I like modelling the body as a right rectangular prism (a cuboid)...No calculations involved.

And I don't think replacing the coboid with a cylinder makes it much more realistic.

If nowadays someone wants to seriously improve on that, he should simulate an animated shape of a actual running human und use collision detection for different rain / wind conditions. This would also provide useful data on which parts are hit by the rain, as they are usually not equaly protected.

 

[jbriggs444]

And I don't think replacing the coboid with a cylinder makes it much more realistic.

I believe that such a replacement is an exact equivalence.

The amount of rain swept out by the forward facing half of the cylinder would be the same as for a cuboid of the same frontal cross-section.

 

[JT Smith]

I believe that such a replacement is an exact equivalence.

The amount of rain swept out by the forward facing half of the cylinder would be the same as for a cuboid of the same frontal cross-section.

I was thinking the same thing when I looked at that paper. So why did they do it? Perhaps it makes a small difference in the case of wind but I doubt that it matters much, if at all, in terms of the overall conclusions. Maybe someone not as lazy as me can verify this.

 

[pinball1970]

There is a Harvard paper on this (http://iopscience.iop.org/0143-0807/33/5/1321)and a simpler one in "the conversation." Apologies if mentioned in the video, not accessed that yet.
Instinctively I run because it at least feels like I am getting somewhere and I also carry an umbrella during rainy season.

(In Manchester rainy season starts at summer showers in mid June, continues mostly to the following March, break for a few days there before April showers hit which consumes most of May. They get some sun in the south East of England apparently.)

 

[A.T.]

Instinctively I run because it at least feels like I am getting somewhere and I also carry an umbrella during rainy season.

And going faster with an umbrella exposes your legs more.

But even without an umbrella, a common case is having a somewhat waterproof jacket, maybe even with a hood, and eventually somewhat waterproof shoes, but almost never waterproof trousers.

 

[pinball1970]

, but almost never waterproof trousers.

I have some and they roll up tight and light. They will be in my rucksack sack tomorrow!

 

[Hornbein]

I like modelling the body as a right rectangular prism (a cuboid). In the absence of wind, the rain will only ever strike the front and top faces. The front face sweeps out a fixed amount of rain regardless of walking speed. The top face is rained on at a constant rate regardless of walking speed. The best strategy is to walk fast so that less time is spent getting the top wet.

No calculations involved.

Well duh. It appears you are right.

 

[JT Smith]

It's a math problem that's being considered here.

A real life anecdote: The other day it was raining lightly. I had on my rain jacket with the hood up. No rainpants or umbrella. I only had to walk for 5-6 minutes to get to the transit station. The jacket and hood protected the horizontal surfaces (top of my head, shoulders) and the brim of the hood shielded my face, at least at my walking speed.

A guy went by on an electric scooter. He was dressed the same as me but was clearly getting hit with rain at a higher rate. He was headed to the same destination and of course got there much more quickly.

When I arrived scooter boy was still there, waiting for the train. My pants had gotten some rain but were basically dry. His looked wet. Different materials maybe? His face also looked wet. Maybe he was sweating.

 

[Tom.G]

I rode motorcycle for many years. One of the questions I would be asked (surprisingly often) was "What do you do when it rains?"

I would casually respond while looking straight at them, "Get wet."

Their apparent cognitive dissonance typically ended the conversation!

Cheers,
Tom

 

[Hornbein]

It's a math problem that's being considered here.

A real life anecdote: The other day it was raining lightly. I had on my rain jacket with the hood up. No rainpants or umbrella. I only had to walk for 5-6 minutes to get to the transit station. The jacket and hood protected the horizontal surfaces (top of my head, shoulders) and the brim of the hood shielded my face, at least at my walking speed.

A guy went by on an electric scooter. He was dressed the same as me but was clearly getting hit with rain at a higher rate. He was headed to the same destination and of course got there much more quickly.

When I arrived scooter boy was still there, waiting for the train. My pants had gotten some rain but were basically dry. His looked wet. Different materials maybe? His face also looked wet. Maybe he was sweating.

He could have been in the rain longer. Splashes too maybe.

 

[anuttarasammyak]

The best is stay at home, especially on Monday morning.

 

[kuruman]

I asked the same question, decades ago, when I was in grad school. I modeled myself as a cylinder and considered the water flux in zero wind. I don't remember the exact calculation, but I remember my conclusion: it is is better to run. Then I took a second look at the answer and thought to myself, "Of course it's better to run, you fool! Why waste time in wet misery when you can spend that time drying yourself indoors?"

Moral: Common sense cannot always be modeled mathematically.

 

[WWGD]

I rode motorcycle for many years. One of the questions I would be asked (surprisingly often) was "What do you do when it rains?"

I would casually respond while looking straight at them, "Get wet."

Their apparent cognitive dissonance typically ended the conversation!

Cheers,
Tom

Problem is if you wear glasses. Then your visibility goes down to 0.

 

[Syed Arif Kamal]

Walk quickly, but not so quick that you risk falling, because the street is wet and friction is less. If you fall you may hurt yourslf, even break bones. Meritorious Professor Dr. Syed Arif Kamal, PhD (Neurophysics)