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Re: one question
On Tue, 28 Nov 1995, Steve VanDevender wrote:
> What I was really objecting to in your parasail design was not
> the idea that you had cancelling momenta, but that you thought
> that creating sideways momentum meant a decrease in forward
> momentum. For example, a device like this:
>
>
> E/c --v :::: p = [ 0 E/(2*c) ]
> |----------------------------------:::/|
> |######~~~~~~~~~~~~~~~~~~~~~~~~~~~~::/ |
> |######~~~~~L~A~S~E~R~~~~~~~~~~~~~~:/ | beam splitter
> |######~~~~~~~~~~~~~~~~~~~~~~~~~~~~:\ |
> |######~~~~~~~~~~~~~~~~~~~~~~~~~~~~::\ |
> |----------------------------------:::\|
> :::: p = [ 0 -E/(2*c) ]
>
> # = laser ~ = laser light -- = wires
>
> also won't move. The beam splitter "absorbs momentum" just like
> the black absorbing plate did, even though it splits the beam
> into two beams traveling in the +y and -y directions. This setup
> also has the advantage of not requiring an unobtainium heat sink,
> as long as you get a Perfect Mirror (tm) from Acme Physics
> Warehouse.
So you're saying that the beam splitter above would move at the same
speed as a absorbtion plate of the same mass?
> > > The wires are indeed under tension, because there is a force
> > > between the laser and the plate. This tension was created in the
> > > first instant the laser was turned on, and a small amount of its
> > > energy went into stretching the wires before it was all spent on
> > > heating the plate.
> >
I've always been taught to view atomic bonds as tiny springs which obey
hookes law F=kx where k is some constant. this is the force that
balances the force of the laser / absorber plate. Is this view correct?
Doesn't a spring provide a constant force as long as it's stretched from
it's initial position?