Yeah...now I can't resist "weighing in"! I had lots of physics in
engineering school myself. The quantity of 20# being placed on the hands is highly suspect
because there are so many variables that make it different for every swing. (I don't
swing with more than a slight weight...I force a reduction by slowing down or subtly
slackening my hold.) But, surprisingly, there is no "doubling."
Think of it this way. Suppose you and your partner were swinging yourselves around a pole
that's fixed to the floor. (Ignore the difference in handhold compared to a dancing
swing.) With the two of you, the pole is in balance and it does not matter if the pole is
even there. Suppose your partner leaves. Your 20# pull, which is now an asymmetrical load,
will now tend to bend the pole (and the pole and its anchor must accept the load), but the
force experienced by your arms has not been reduced by half.
Date: Wednesday, September 07, 2011 4:26:35 am
To: "Caller's discussion list" <callers(a)sharedweight.net>
From: "Donald Perley" <donperley(a)gmail.com>
Subject: Re: [Callers] Swinging
Sigh... time to drag out the free body diagrams and unstretchable
massless string. 20 pounds.
On Tue, Sep 6, 2011 at 9:53 PM, Jeff Kaufman <jeff(a)alum.swarthmore.edu> wrote:
Mark Widmer wrote:
> each person exerts 20 pounds on the other person, and nobody is
> exerting 40 pounds.