I heard recently that if you run in the rain than you would get more wet than if you walked in the rain. Do you think this is true? If so, what is the optimum speed to stay the dryest?
2006-06-14 06:42:47 · 10 answers · asked by Mr. Hendricks 4 in Science & Mathematics ➔ Physics
the optimum speed is infinitly fast...
In reality I did a simple model of it and it turned out to be a good paced jog
here is the answer I gave befor... Try the model and see what you think
This is actualy a very interesting question. It depends on the speed at which you move and the direction of the rain.
Clearly if there is a wind blowing in the direction that you are going to get more wet if you move slower than the wind than if you move at the same rate at the wind.
But for now let us assume that the rain is comming strait down at a constant rate. No matter what speed you are moving the ammount of drops per second that hit the top of your head is going to be constant. it is the question if how many drops hit the front of your body.
If the flux(phi) of the rain is phi=10 (the ammount of drops that pass through a unit area in a second) then no matter what you are going to have 10 drops times the area of your head hit your head every second. As for your body the geomotry can be worked out and you can see that you will be hit by phi*tan(V/V_r) time the area of your body, where V is your speed, and V_r is the speed that the rain is falling.
So the question is what is the optimal speed to move in the rain in order to get the least ammount of drops to hit you. To get the total amount of drops that will hit you you take the total number of hits a second (phi * tan(V/V_r) * A_b + phi * A_h) and multiply it by the amount of time that you spend in the rain.
This is a very crude model. But assuming that the area of you body is about 15 times biger than the are of you head, you should travel at about 70% the spead at which the rain is falling. If you assume that the rain falls at about 10 m/s, you should be going 14 m/s. Which is running at a pretty good pase.
Now, I do not know the speed that rain falls and I think I used a rather low number there, so I would say that it is better to run in the rain.
2006-06-14 06:57:36 · answer #1 · answered by farrell_stu 4 · 4⤊ 2⤋
Faster is dryer. Try it yourself. Run from one house to another in the rain as fast as you can and see how wet you get. Now walk VERY VERY slowly back, taking 5 or 10 minutes to get there, and you will be soaked.
The speed doesn't matter argument says that as you run, you "sweep up" raindrops that would not otherwise have fallen on you and the volume of raindrops "swept up" does not depend on speed, only your cross sectional area and the distance you travel. But that argument ignores the rain that does fall on you when you are standing still, and that DOES depend on how long you are out in the rain. So by running fast you are having no effect on how much extra rain you "sweep up" but you are minimizing the time you spend out in the rain.
2006-06-14 07:51:41 · answer #2 · answered by campbelp2002 7 · 0⤊ 0⤋
Assuming you are not protected by any rain gear or umbrellas and the rain is consistent in drop size and is coming straight down. It should be obvious that the faster you go the fewer rain drops will strike you. If you stand still, you will be struck by rain drops until it stops raining;however, it you can move infinitely fast then the number of drops that will strike you will be the least because you will be in the rain for the least time.
I did not see the MythBuster show, so I don't know their methodology or their criteria for measuring the degree of wetness but I suspect it was not ideal as an experiment
2006-06-14 07:33:55 · answer #3 · answered by oil field trash 7 · 0⤊ 0⤋
Run as fast as possible. Consider two extreme cases:
1. You STAND in the rain. Your travel time is infinite, and therefore your wetness is infinite.
2. You travel at lightspeed, arriving home before even a single drop moves as much as a millimeter. In your run, your body has intercepted a volume of rainy air equal to the cross-section of your body times the distance travelled. You get wet, but much less wet than when you stand. And there is no way to intercept any LESS water than that by travelling slower.
2006-06-14 07:28:09 · answer #4 · answered by Keith P 7 · 1⤊ 0⤋
Mythbusters from Discovery Channel took that issue on and proved that running and walking in the rain would get you equally wet. Check their site, and I think you can get that answer.
2006-06-14 06:47:04 · answer #5 · answered by Sergey and Roxanna K 2 · 0⤊ 0⤋
It not only depends on your speed but also how your body is oriented with respect to the falling rain.
2006-06-14 06:47:08 · answer #6 · answered by ag_iitkgp 7 · 0⤊ 0⤋
If you run in rain you will wet more at your front side
2006-06-14 07:13:05 · answer #7 · answered by --> ( Charles ) <-- 4 · 0⤊ 0⤋
3-5 kms per hours
2006-06-14 06:51:25 · answer #8 · answered by pravs 1 · 0⤊ 0⤋
When you run you kick so much more water onto yourself what's the point?! Just get wet - you won't melt...
2006-06-14 07:02:57 · answer #9 · answered by Jon 1 · 0⤊ 0⤋
well I think you recieve the same amount of water, but you get to where your going faster if you run.lol
2006-06-14 06:47:59 · answer #10 · answered by raider_way 3 · 0⤊ 0⤋