[ExI] A Lawn sprinkler

spike spike66 at comcast.net
Wed Jun 13 05:25:39 UTC 2007

I know the answer!  I built such a device and tried it after reading
Feynman's book Surely You're Joking Mr. Feynman in the spring of 1986.  I
won't tell just yet, but I will volunteer that none of my fellow undergrads
had it completely right beforehand.


> -----Original Message-----
> From: extropy-chat-bounces at lists.extropy.org [mailto:extropy-chat-
> bounces at lists.extropy.org] On Behalf Of John K Clark
> Sent: Tuesday, June 12, 2007 10:19 PM
> To: ExI chat list
> Subject: [ExI] A Lawn sprinkler
> You pump water through an S shaped lawn sprinkler and it spins
> counterclockwise, but suppose you put the sprinkler in a tank of water and
> pump water out not in. What direction will the sprinkler rotate? As an
> undergraduate Richard Feynman actually tried the experiment but he was not
> successful; the tank burst flooding the lab and he almost got kicked out
> of
> school. However he later figured out what the answer must be.
>  John K Clark
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