Run vs. Walk controversy

Cecil's Columns/Staff Reports
1

OK, look, I was reading the raining thing and if it was better to run than walk (under the Straight Dope classics) and I found this piece of information;

“One obvious caveat. If enough rain falls on you, whether because of the intensity of the rainfall or the distance you have to travel, eventually you’ll be thoroughly soaked. After that it doesn’t matter whether you run or walk; you’re as wet as you’re going to get.”

Well it does matter, especially if it is a cold wet rain day whereas if it was warm drops coming down it wouldn’t really matter. See the point of getting out og the rain is (1) to not get wet and (2) to not get cold and therefore be more comfortable. of course if you are wet then you are cold (I am assuming the cold day thing) and you are only cold because it is cold around you. Your body heat will warm up the drops that hit you but if more COLD drops are coming down on you then that body heat is being wicked away. Cecil was wrong. It does matter if you run or walk AFTER you are soaking wet.

2

Cecil was commenting on whether you would get more wet by walking or running. He was not commenting on whether you should stay out in the rain at all, nor the comparative comfort of indoor (dry, warm) and outdoor (wet, cold).

If it comes to that, clearly you remain driest and warmest by not going outdoors at all. But what kind of answer would that have been?

3

I’d argue that Cecil’s answer, while correct, is obvious to anyone who’s ever experienced rain. What’s more interesting to me is the “alledgedly larger number of chest drops.” That is, the answer to this slightly different question:

“If person A and person B are in the rain for THE SAME PERIOD OF TIME, will the runner (A) get wetter than the walker (B)?” This assumes that they’re going different distances, of course.

I suspect the answer is “yes,” but that’s just me. I’m also not sure I buy the assertion that the number of head drops is the same (per unit time) for both parties, so when Cecil goes out to test this, have him wear a pointy contruction-paper hat, would you?

4

I suspect the answer is “yes,” but that’s just me. I’m also not sure I buy the assertion that the number of head drops is the same (per unit time) for both parties, so when Cecil goes out to test this, have him wear a pointy contruction-paper hat, would you?
]]]]]]]]]]]]
Not going to loan him mine…

5

If it’s dry outside and starts to rain, most people would start to run to a dry area. Maybe cause when it starts to rain, rain mainly falls straight down. However, with wind, rain falls angular.

If its falling at an angle that hits your back first, you could run and stay dry. If its angular puts it that it hits your chest first, then running would make one more wet.

6

This problem seems difficult only because we are examining two people whose speed is relatively close, on a cosmic scale.

Consider the extreme cases. The runner runs at near-instantaneous speed. He collects those drops currently between him and the car. If he doubles or halves his speed, it will have almost no effect

Now assume a lo-o-o-ong rainstorm, and walkers who moves at less than a yard an hour. Clearly the amount of rain they collect is almost a direct result of the time they spend in the rain. The inch an hour walker is hit by about twelve times as much rain as the foot an hour walker. As the walkers speed up, they get less total rain, although the faster they get, the less linear the relationship, due to those pesky drops that one runs into. Note that the runner at 90,000 miles per second collects almost exactly the amount of rain that the runner at 180,000 miles per second collects, since each gets almost exactly those drops that are already between them and the car.

(We ignore the runner who is twice as fast as the 180,000 miles-per-second runner, for reasons that don’t bear going into.)

Conclusion: There is a minimum amount of water one must receive, regardless of speed. Slowness can add to that amount. To put it in simple terms, the longer one spends out in the rain, the wetter one gets.

Why is this hard to understand?

7

[[ “If person A and person B are in the rain for THE SAME PERIOD OF TIME, will the runner (A) get wetter than the walker (B)?” This assumes that they’re going different distances, of course. ]]

Yes. Imagine that the top view of our people looks like a plate (circular and flat). If I hold the plate still with the flat surface facing up, a certain number of raindrops will hit during each period of time. If I move the plate, then it moves out of the way of the drops coming down behind the direction of motion, but it moves under the drops ahead of the direction of motion. In the end, the number of drops that hit the plate from the top is independent of whether or not the plate is moving.

Now, if I attach a cylinder to the bottom of the plate (so our two people are modelled like paper towel rollers with caps on the ends), then as long as the cylinders remain still, no rain hits the sides (it all hits the top). As soon as one of the cylinders begins moving, it starts running into the raindrops that were falling harmlessly beside it when it was still. Assuming that the drops have reached a terminal velocity as they pass from the top of the cylinder to the bottom, the number of drops that the cylinder will run into is directly proportional to the speed. Meanwhile, the number of drops that hit the plate on the top remains constant.

Perhaps an even more interesting question is what happens if the two people travel through the rain for the same distance (say, from a building to a car), but one is running and one is walking. The runner gets hit with more rain than the walker in the time it takes her to run to the car. The walker, on the other hand, has been hit with less rain than the runner when the runner gets to the car, but the walker still has to walk the remaining distance to the car. Obviously, if the walker was standing still, she would eventually be hit with alot more rain than the runner, and if she moved at the same speed as the runner, she would be hit with the same amount.

To express this mathematically (it’s not that complicated, so bear with me here) let the distance to the car be D, the speed that a person moves be S, and the time it takes to get to the car be T. These three values are related: D = S*T.

Next, let A be the amount of rain that hits our people from the top every second, and S*B be the amount of rain that they run into (ie that hits their cylindrical sides) every second (remember that the amount of rain they run into is proportional to speed, thus the S term). Let the the total amount of rain they get hit with be R, and we can relate all these terms:

   R = A*T + S*B*T

Now, since T = D/S, we can substitute for T and get R in terms of S:

   R = A*D/S + B*D

This is a pretty cool result, because it lets us see that the amount of rain the people run into (the B term) is constant. Since both people have to move the same distance, they both run into the same amount of rain (the B term). On the other hand, by moving faster, the runner increases S and reduces the A term, and thus gets hit with less rain.

Returning to the first equation, we can see that if the time spent in the rain is the same for both people, then the one standing still will be hit with less rain.

Moral: If it’s going to stop raining before the runner gets to the car, then you’ll do better by standing still until the rain stops, then walking to the car. On the other hand, if the rain isn’t going to stop before you get to the car, you’re better off running. Weather prediction being what it is, I’d take my chances and run.

– Mike –

8

There was actually a study on this. Two similar sized people were sent out in the rain on the same path, one walking and one running. The clothes they were wearing were wieghed before and after, the difference being the amount of rain water soaked into the cloth. The person that ran had less water absorbed. But then this is just common sense. If you don’t want to be rained on, get to shelter as fast as you can.

9

Okay I’m specifically writing in response to Jay. While Jay may have a lot of fun running around in the rain at 180,000 feet per second I personally can’t do that. However Jay says that there is no difference between running 90,000 feet per second and 180,000 feet per second. He’s right. But he brings a large misconception into play. Just because there is no difference between those two doesn’t mean there is no difference between 90,000 and 10,000. I’m sure that if you were running 90,000 feet we can all realize that someone who would get there in one second is going to be hit by fewer rain drop that the person who gets there in 9 seconds.

Issue number 2: Head drops versus chest drops…and other angular things. I prefer to walk in the rain…maybe it’s because I don’t mind getting wet. Maybe it’s just because I’m lazy. No matter. I like it when my hair gets wet but absolutely hate it when my clothes get wet. Henceforth I can come to the conclusion: head drops are better than chest drops because once you are wet you can’t get any wetter. Seeing as how the area of one’s head is generally smaller than the area of one’s chest or back we can see that once enough head drops have hit us to cover our head it won’t get any wetter. So if you have to get more head drops to avoid the chest drops…go for it.

Issue number 3: The administrative person who replied to the first one obviously didn’t read it all the way through. While he/she thinks it is regarding indoor/outdoor comfortability what they were really saying was: Are we measuring how wet you get or how comfortable you are. This brings into play the fact that wet people who run through cold atmospheric conditions…get colder. People who walk however, remain confortably cool.

Conclusion: Run if you don’t mind your clothes getting soaked and catching a cold. Walk if your like me, lazy and sensible.