Waste less time on Facebook — follow Brilliant.

Would you walk, or run, in rain?

You're walking home from school and there is a sudden downpour. You immediately start running but the raindrops strike you relentlessly. You run faster... and faster... and faster. You realise that now, not so many raindrops hit you on your head, but instead, you're colliding head-on with the raindrops. As you approach the speed of light, the raindrops move slower until finally they appear frozen in time. But you still collide head-on with the raindrops.

As an example, @Yuxuan Seah and I were running to the canteen after swimming class on Thursday. Yuxuan ran with his usual rocket speed and I ran at about two-thirds of that speed. I appeared about 3 times as wet as he was :P

So basically,

1) Is there an optimal speed to run when it is raining?

2) How fast would that be?

3) Would the angle of the rain falling affect this speed? Are there any other factors? (EDIT: When I said "other factors", I really didn't mean "presence of an umbrella")

4) what if it were hailing instead? Do the size of the particles matter?

Note by ZhiJie Goh
2 years, 4 months ago

No vote yet
1 vote


Sort by:

Top Newest

Depending on your running speed, whether you have an umbrella or not and many other factors, optimal speed will vary. But if all those technical bits confuse you, just follow my (and William Poundstone's in his book Are you smart enough to work at Google) advice: Walk if you have an umbrella, run if you don't!

I like the fact you mentioned me in your example though :D @ZhiJie Goh Yuxuan Seah · 2 years, 4 months ago

Log in to reply

Well, if you run fast you would be saved from the drops hitting you from above but you would get hit by the drops from the side...In your case, Yuxuan Seah did not get as wet as you because there wasn't much water around you on the streets to make him wetter...You got wet because you ran slow and were hit by more amount of raindrops falling from above...

No, I don't think that the angle of the rain would affect the amount of wetness... Case I: Rain is falling vertically downward:- If you run and are saved from the volume of rain directly above you, you would be hit by the same volume, next instant.

Case 2: Rain falls at an angle:- If the rain falls at an angle, the only difference would be that you would need to keep your umbrella at an angle. Other than that, the volume of rain hitting you would be same (Neglecting that you grew hefty in some days :D), but the volume would be hitting you at an angle, either from front or from behind. That's it!

Cheers!!:):) Abhineet Nayyar · 2 years, 4 months ago

Log in to reply


Problem Loading...

Note Loading...

Set Loading...