## PSN-L Email List Message

Subject: Re: Zero-length spring
From: "chief.cook.nz" chief.cook.nz@............
Date: Sun, 03 Dec 2006 03:30:16 +1300

```Hi John
In this formula a NEWTON is what?  or how or why is called a NEWTON the rest
I understand so a

NEWTON:- =

Cheers Tamati
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From the Castle of Tom, Robyn and the Dog

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----- Original Message -----
From: "John or Jan Lahr"
To:
Sent: Thursday, November 30, 2006 8:20 PM
Subject: Re: Zero-length spring

> At 10:29 PM 11/29/2006, you wrote:
>>Hi John,  I am not too good at math, could you please plug-in some
>>examples/numbers for this formula so I can understand it better? I think
>>its k that I am unclear of.  I understand the rest. Thanks, Ted
>>MgA = kSY/(SA)
>>
>>M = kY/(Ag)
>
> k is the spring constant.  In this example I'm using k = 2 newtons/cm
>
> M is the mass
> Y is the height of the mast
> A is the length of the boom
> g is the acceleration of gravity
>
> The exact numbers don't really matter - the point being that the mass will
> be stable at any angle of the boom.
>
> There are problems of trying to actually build this device, because slight
> changes in k with temperature will cause instability.  Even without a
> zero-length spring, one can extend the period by reducing the height of
> the mast.  However, you will soon discover that this will also lead to
> instability if pushed to too long a period.
>
> Cheers,
> John
>
>
>
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