Subject:
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Re: Robotic Wheelchair
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 2 Jul 1999 19:12:49 GMT
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Viewed:
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796 times
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But *catching* 25 lbs of lead is different than catching 25 lbs of
feathers. The G forces during impact (which in turn affect the forces
needed to maintain balance) vary tremendously depending on the shape,
size, and compressive properties of the object. Think of it this way -
both objects (when falling from the same height) have the same amount of
kinetic energy. Presumably the lead doesn't compress much, so if it hits
a rigid surface all of the kinetic energy must be absorbed in a very short
amount of time. This means a large force over a short period of time.
The feathers, on the other hand, would presumably compress on impact (I'm
assuming a large bag - not compressing the feathers into the smallest
possible space), yielding more time to disperse the same amount of kinetic
energy. This means a smaller force applied over a longer period of time.
From a robotics standpoint, the hard impact is tougher to maintain
balance.
Of course the occupant of the wheelchair could always compensate (keeping
his arms loose as he caught the lead, etc).
Anyway, I hope I didn't stray too far off-topic for something that was
probably just a humorous post to begin with.
Dave
In article <377CF590.D23F2DA5@earthlink.net>, Phil Watt
<wattsup1@earthlink.net> wrote:
> 25 lbs is 25 lbs
>
> -S.I. Newton
>
>
> Nick Goetz wrote:
>
> > Most definitely. Since the 25lbs of lead is heavier it was more impressive.
> > But now that I think about it, they never did show what was in the bag. It
> > might have been a trick.
> >
> > -Nick
> >
> > Kekoa Proudfoot wrote in message ...
> > > rmtmd <rmtmd@concentric.net> wrote:
> > > > Watching it climb stairs was impressive, but seeing the chair stand
> > > > upright on two of its four wheels while the occupant caught a 25lb sack
> > > > of lead, all without the robotic chair even appearing to correct its
> > > > balance was amazing.
> > >
> > > Hrm. I wonder if things would have been different if the occupant had
> > > caught a 25 lb sack of feathers? Probably.
> > >
> > > -Kekoa
--
reply to: dbaum at enteract dot com
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Message has 1 Reply:
 | | Re: Robotic Wheelchair
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| Thanks Dave, for this rather complete and clear explanation of what I alluded to. In case anyone misunderstood me about feathers being easier to catch. Dave explained it much better. (...) yeah. we did. :) (25 years ago, 2-Jul-99, to lugnet.robotics)
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