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A gentle rain....

Suppose that a gentle rain is falling at a rate of 1 inch per hour straight down.  A person is in a car that is 100 feet from the entrance of a building....

The question is: If the person was to run twice as fast as they could walk to the building, would they get half as wet as if they walked to the entrance of the building? Also at what theoretical walking or running speed would the person get the least wet and the most wet supposing that they must ultimately get to the inside of said building?

Note: Some may consider 1 inch per hour more than a gentle rate of rain; however, here in the Midwest some consider any rate of rain gentle as long as there isn’t a wind accompanying the rain….. ;^)

Budd
Friday, June 04, 2004

First of all, I doubt that this is the answer that you are looking for.  Your question looks like you're looking for equations that involve vectors or for some simple aha-type answer.  Nevertheless, here is what I think.

In general, I think your degree of wetness (assuming a consistent rainfall with no wind) is contingent on how long you are exposed to the rain, your surface area normal to the rainfall, the amount of accumulated puddles.

Thus, I would use an equation like this:

wetness(t) = 1 in. / hr * (distance/running speed) * (surface area normal to rain) + (puddle accumulation rate) * (coefficient of how wet a puddle makes you) * (distance/running speed).

Here, distance/running speed is how long it takes to get from the car.  The surface area normal to rain should be proportional to the running speed (if you run more quickly, you tend to have a longer stride). 

Determining the coefficients is left as an exercise to the reader (or maybe I'll work them out at a later time.)

dejavujade
Saturday, June 05, 2004

According to the television show MythBusters, you get just as wet (if not wetter) running as opposed to walking a fixed length.

http://dsc.discovery.com/fansites/mythbusters/mythbusters.html

Matt Brown
Monday, June 07, 2004

Also, check out a three-part article here: http://www.dctech.com/physics/features/0500.php

dejavujade
Monday, June 07, 2004

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