Physicist Reveals Why You Should Run in The Rain (sciencealert.com) 27
Theoretical Physicist Jacques Treiner, from the University of Paris Cite, explains why you should run in the rain: ... Let p represent the number of drops per unit volume, and let a denote their vertical velocity. We'll denote Sh as the horizontal surface area of the individual (e.g., the head and shoulders) and Sv as the vertical surface area (e.g., the body). When you're standing still, the rain only falls on the horizontal surface, Sh. This is the amount of water you'll receive on these areas. Even if the rain falls vertically, from the perspective of a walker moving at speed v, it appears to fall obliquely, with the angle of the drops' trajectory depending on your speed. During a time period T, a raindrop travels a distance of aT. Therefore, all raindrops within a shorter distance will reach the surface: these are the drops inside a cylinder with a base of Sh and a height of aT, which gives:
p.Sh.a.T.
As we have seen, as we move forward, the drops appear to be animated by an oblique velocity that results from the composition of velocity a and velocity v. The number of drops reaching Sh remains unchanged, since velocity v is horizontal and therefore parallel to Sh. However, the number of drops reaching surface Sv -- which was previously zero when the walker was stationary -- has now increased. This is equal to the number of drops contained within a horizontal cylinder with a base area of Sv and a length of v.T. This length represents the horizontal distance the drops travel during this time interval. In total, the walker receives a number of drops given by the expression:
p.(Sh.a + Sv.v). T
Now we need to take into account the time interval during which the walker is exposed to the rain. If you're covering a distance d at constant speed v, the time you spend walking is d/v. Plugging this into the equation, the total amount of water you encounter is:
p.(Sh.a + Sv.v). d/v = p.(Sh.a/v + Sv). d This equation proves that the faster you move, the less water hits your head and shoulders, but the amount of water hitting the vertical part of your body remains constant. To stay drier, it's best to move quickly and lean forward. However, you'll have to increase your speed to offset the exposed surface area caused by leaning.
p.Sh.a.T.
As we have seen, as we move forward, the drops appear to be animated by an oblique velocity that results from the composition of velocity a and velocity v. The number of drops reaching Sh remains unchanged, since velocity v is horizontal and therefore parallel to Sh. However, the number of drops reaching surface Sv -- which was previously zero when the walker was stationary -- has now increased. This is equal to the number of drops contained within a horizontal cylinder with a base area of Sv and a length of v.T. This length represents the horizontal distance the drops travel during this time interval. In total, the walker receives a number of drops given by the expression:
p.(Sh.a + Sv.v). T
Now we need to take into account the time interval during which the walker is exposed to the rain. If you're covering a distance d at constant speed v, the time you spend walking is d/v. Plugging this into the equation, the total amount of water you encounter is:
p.(Sh.a + Sv.v). d/v = p.(Sh.a/v + Sv). d This equation proves that the faster you move, the less water hits your head and shoulders, but the amount of water hitting the vertical part of your body remains constant. To stay drier, it's best to move quickly and lean forward. However, you'll have to increase your speed to offset the exposed surface area caused by leaning.
Umbrella (Score:4, Informative)
Use an umbrella. Duh.
Re: Umbrella (Score:2)
Re: (Score:1)
But my umbrella always inverts when I run in the rain!
Re: Umbrella (Score:2)
Re: (Score:3)
You're holding it wrong. (Score:2)
>> But my umbrella always inverts when I run in the rain!
You're holding it wrong.
Angle it against the wind.
Or to put it another way (Score:2)
The quicker you reach shelter the drier you'll be. If you stay out in the rain it doesn't matter how you move you'll get just as wet, it'll just be on a different part of your body.
Did they factor in the chance of slipping? (Score:3)
The MBA factor. (Score:2)
If you run it's more likely you'll slip and get full-blown wet. That's not factored in, so, back to your equations, Dr Treiner...
We've just been given a running recommendation, from an expert who understands everything, and yet nothing.
Hell. I’ve never seen a finer example of an MBAs actual value.
*$350/hr. golf clap*
TL;DR - This.
Superman... (Score:2)
You fly in a superman orientation infinitely fast. Then the only raindrops that hit you are those that were blocking your route.
For light rain it's possible to dodge the raindrops completely.
For heavy rain and a sufficient distance it's best to go vertically until you're above the clouds.
Re: (Score:2)
The water hitting the vertical part of your body stays the same regardless of speed
That intuitively seems false, but I can't figure out the math (the notation is weird, which doesn't help). I read the article several times, and I don't understand the logic of this physicist. The organization of the article is horrific. For example, this sentence:
Let p represent the number of drops per unit volume
What is "unit volume?" Volume of what? The only other use of the word "unit" in the entire article is unit of time!
Re: (Score:2)
'Per unit volume' is used all the time in cases where the exact unit doesn't matter, other than it being volumetric. 15,000 raindrops per cubic meter, 120 raindrops per cup, etc. Outside of my field, I think the most I've ever seen that term used is to define density: "Mass per unit volume".
As far as the first point goes: Try envisioning a horizontal rectangle with a constant amount of dots in it, where the dots move downward from the top at a constant rate at a random point along the x-axis, with a bar swe
Mytbusters did this one (Score:3)
They came to the opposite conclusion but they were test IRL [youtu.be] and not just theorizing.
Re: (Score:2)
MythBusters would like a word (Score:3)
MythBusters did this very experiment [youtube.com] a while back. According to their experiment, running increases the amount of rain falling on you compared to walking.
Re: (Score:2)
is this per fixed time, or per fixed distance ?
Next up (Score:2)
Some research on running with scissors.
Of course, the form you have to sign to participate is a bit longer ...
once while riding a motorcycle (Score:2)
He got it all wrong... (Score:2)
Re: (Score:2)
Re: (Score:2)
Terrible science (Score:2)
What about the drops of water splashing back up off the ground which will increase when you start walking/running?
Someone kill the blurb's author (Score:2)
Physicist Reveals HOW You Should Run in The Rain
HOW you should run in the rain. Not WHY. What sort of raving incompontent produces this drivel and... .oh, wait. This is one of those AI blurbs isn't it.
Journalism, and communication, is dead. This is our dystopian future.
no use (Score:3)
no use to complain,
when you're caught out in the rain,
your mother's quite insane.
cat food, cat food, cat food, again?
Usually that's when (Score:2)