4 Sep
2011
4 Sep
'11
10:49 p.m.
lol. thank you, jeff. i'm sure that's exactly how i meant to explain it!!
but actually, you make a great point. when i think of the most satisfying swings i've
had, centrifugal force is a GREAT part of it. that's why leaning back doesn't
make sense - you should pull in. centrifugal force pulls you back - no need to do it
yourself. in fact, i think that counteracting centrifugal force by pulling in is what
makes the most satisfying swings seem totally effortless. balance IS the key.
barb
Date: Sun, 4 Sep 2011 18:35:23 -0400
From: jeff(a)alum.swarthmore.edu
To: callers(a)sharedweight.net
Subject: Re: [Callers] Re Swinging
John Sweeney wrote:
I think you must be talking about much slower swings than I'm talking
about. Let's say we have two 130 pound people who swing 3.5 times
around in a balance and swing. Physics geekery [1] says it takes
fourty pounds of force to hold the two of them together. I'd much
rather have that split over two people.
Jeff
[1] Let's approximate the dancers as point masses of 130 pounds nine
inches apart. There are 12 counts of swinging after the balance,
so about six seconds. Rotating 3.5 times in six seconds means 35
times in sixty seconds, or 35 rpm. Force here is M*w*w*r, where
M is 130 pounds, w is 35rpm, and r is 4.5 inches. This gives
20lbf for each dancer, or 40lbf total.
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If the lady additionally has their left hand on
the back of the
the gent's right shoulder, then the lady is doing more of the
holding together and the gent can do less.
Centrifugal force is not that great - if you are in balance the
pressure is tiny.