[Tango-L] Strong Lead - resistance effect

[Daniel Lakeland]

On Wed, Sep 26, 2007 at 01:11:42AM +0300, Krasimir Stoyanov wrote:
> ----- Original Message ----- 
> From: "Daniel Lakeland" <dlakelan at street-artists.org>
> To: <tango-l at mit.edu>
> Sent: Tuesday, September 25, 2007 11:20 PM
> Subject: Re: [Tango-L] Strong Lead - resistance effect
> 
> 
> 
> > The bodies act 'as if' a force is acting
> > between them, but not because the leader is applying a physical force
> > to the follower.
> 
> REALLY? Isn't there a simpler explanation? That the bodies DO experience a 
> force in-between?

No, for two reasons. First, I and others frequently dance with
partners using no physical connection, to practice both follow and
lead, and second, the forces required to synchronize two bodies moving
in the way that tango dancers do would be very strong and unpleasant
when applied across the arms of the embrace.

Definitely, tango dancers in an embrace transmit forces between the
two bodies, but these forces are signalling, not the principle forces
required to synchronize the bodies.

For example: 

A 70 kg rigid sack of potatoes on ice (a model for a follower being
forced around) is accelerated from rest to .5 m/s in an interval of .5
seconds and then back to rest in another .5 seconds. The impulse in
each interaction is 35 N-s and the average force is 70 N. The peak
force must be more than the average force. Perhaps 1.5 times as much
is a reasonable guess. So are you first pushing your partner with 105
N of force and then pulling her back to stop her? This is about 25
lbs. Try dead-lifting a 25 lb (~ 100N or 11kg of mass) weight and then
come back and tell me if you're applying that much force to your
follower.

I suggest the answer lies in between that and zero. Perhaps 5 lbs of
force on average, with the follower supplying the rest of the lateral
forces required using her legs (surely we must acknowledge the keen
importance of the followers legs!)

Yes, forces are transmitted, and occasionally during vigorous turns
and soforth they may approach my example of 100 N or 25 lbs, but on
average they are much below this.


-- 
Daniel Lakeland
dlakelan at street-artists.org
http://www.street-artists.org/~dlakelan