Is it Better to Walk or Run in the Rain?

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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!

Thanks to Nima Doroud for contributions and to Perimeter Institute for support.

Created by Henry Reich Created by Henry Reich

[roninyasuo]

Never thought I'd use: "Wetness per second, " as a measuring unit.

[trr]

I stood in the rain for two hours trying to calculate the fastest way to get to my house that is 10 meters away

[samirpernell]

That was the longest "running is better" I've ever heard

[varmituofm]

There's a lot of complications to this problem. You assume that rain falls directly down, but most rain is accompanied by wind. Now, rain hitting you side is a function of time, distance, and speed (if you exactly match the speed of the wind, no rain will hit you from the side). Turns out, the best strategy into the wind is maximize speed, and with the wind you want to be a bit faster than the wind.

[TheRoboticLlama]

before watching this video: obviously running is better.

after: running is better, but now I'm confused

[lgtv]

99.9% scientists recommend using a umbrella

The other 0.1%:

[StickManShortsofficial]

It's been 15days and I am still standing in the rain.. trying to stay dry...now that I watched this video. I am going home.
Thanks. 🙏🏻

[stephenj]

I've honestly wondered about this my whole life, but couldn't figure out the maths behind it. Moving upward into the rain is a great visual.

[elilunwell]

"9 out of 10 scientists recommend this umbrella"
_That one scientist:_

[dude]

I was fearing he would say last minute: "so the best solution is to use an umbrella" after all the math he explained XD

[saraswatibaisoya]

Looks like youtube recommendation brought us all together again

[jokingii]

This is amazing, I’ve had this exact theory for ages now, but always felt like I was making stuff up when I was telling other people. Until today. Seeing it actually be proven true feels so validating.

[olakolade]

At this point i'm just watching whatever youtube puts in my recommendations.

[iknowimstupidwhenisaythisb]

*Walk or run in the rain*
Wind: im about to end this man's whole career

[redountilgreat]

No joke - I've asked myself that question for years. The answer was really fulfilling to hear. Thanks

[_wetmath_]

i think there's another factor that isn't mentioned here. when you stand still, your average cross sectional area (where raindrops will hit you from the top) is the minimum. but when you run, you lean forward, which increases your cross sectional area and expose your back and legs to rain too.

to minimise rain, you should therefore try to run while remaining as upright as possible. however, this limits your top speed because it's harder to balance. so it's not immediately obvious how fast you should run.

practically, i think maintaining balance (so you don't slip and fall), uprightness (to minimise vertical rain), and speed (to minimise time spent in the rain) would be the most effective. lean a little forward while still running at a good pace AND try not to slip.

[pablotorres]

Every time I see this in my recommended I watch it again because I keep forgetting

[alexandrerohban]

Moral of the story: never forget your umbrella...

[morlnsk]

"Math will help you in real life".
Math in real life:

[jami.m]

Reality math is always cool, but you should consider adding the angle of the raindrops to your equation. They almost never fall straight down. Just a slight wind from different angles could change the equation a lot.