The AFU and Urban Legend Archive
Science
 terminal velocity equation




Newsgroups: alt.tasteless,alt.folklore.urban
From: bml@netcom.com (Brian Leibowitz)
Subject: Re: Pancake corpses
Date: Fri, 10 Jun 1994 15:00:20 GMT

In article <2t84va$iad@panix.com> dannyb@panix.com (danny burstein) writes: >Having seen far too many of these, inclding some from 30-40 stories up
>which gets you (or rather them) pretty close to terminal velocity
>
>(40 stories= 400 feet. L=1/2AT^2. 400=1/2AT^2. 800=AT^2. 800/32=25
>25=T^2, T=5. velocity=32*5=160feet per sec = approx 110 mph/200kph)

Yes you get close to terminal velocity, but the equation you use is not valid when you have significant air resistance.

You need to use:
v = (g/c)(1-e^(-tc))
The constant c is about 0.394 sec^-1. Integrating and solving for initial conditions gives:
x=[integral] vdt = (g/c)(t + (1/c)(e^(-tc) -1))

For the example found in Christine Lavin's song _Doris and Edwin_ [I did this and another silly calculation for Christine many years ago] Edwin is travelling about 113 mph after falling 32 stories (I used 420 feet assuming higher ceilings) and it takes about 7.55 seconds.

[equation for v(g,c,t) and constant are from the book _Physics volume 1_ by Paul A. Tipler]

Brian "Will dig out the old freshman physics books for someone

who gives me free concert tix" Leibowitz


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