Path: chuka.playstation.co.uk!news
From: sosman@terratron.com (Steven Osman)
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: angular acceleration
Date: Wed, 08 Dec 1999 22:52:33 GMT
Organization: PlayStation Net Yaroze (SCEE)
Lines: 56
Message-ID: <384fe0ab.11649370@news.playstation.co.uk>
References: <825q0v$gu11@chuka.playstation.co.uk>
NNTP-Posting-Host: 209.27.57.69
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Newsreader: Forte Agent 1.5/32.452

Jon,

Off the top of my head, everything you're saying is correct...
However, I think what MAY be incorrect about your conclusion is that
you can output maximum torque instantly.  I don't know that the
muscles in the arm react THAT quickly (especially with no significant
resistance to warrant it).

Again, this is purely guessing...

Steven

On Thu, 2 Dec 1999 12:51:55 -0000, "Jon Prestidge (Moose)"
<jon@surfed.to> wrote:

>Is anyone familiar with the formula to calculate angular acceleration
>from torque and moment_of_inertia ...
>  or, more to the point, the appropriate units to use?
>
>I think it is:-
>
>  angular_acceleration = torque / moment_of_inertia
>
>... if torque is in Newton_metres and moment_of_inertia is in
>Kg * metres_squared, then what is angular_acceleration in?  Is it
>in radians_per_second_per_second ?  I'm just a bit sceptical it could be
>that simple!
>
>If so does this example look about right?...
>
>I'm working through an example of lifting-up my straight arm as fast as I
>can.
>I reckon the max torque of my sholder in that direction is about 68Nm
>and the moment_of_inertia of my straight arm about the axis of my sholder
>is about 0.937 Kg * m_squared.  So...
>
>  angular_acceleration = 68 / 0.937 = 72.57
>
>so if it was 72.57 radians_per_second_per_second it would equate to
>4158 degrees (or for the playstation 47308 1/4096ths)
>
>So (ignoring gravity) I could lift my straight arm from down by my side
>upto horizontal, which is about a quarter arc:-
>( if I could do 72.57/1.57 = 46.199 quarter arcs per_second_per_second )
>I could achive the quater arc in 0.022 of a second?  That seems too quick.
>
>
>
>Jon Prestidge
>
>P.S.  I've got a list I've compiled of typical max torques for each joint
>in the body, which any one is welcome to ( just mail me jon@surfed.to ).
>Be warned though, it is not tried and tested data, it is data from
>me and bathroom scales and a few sprained muscles.
>