Re: basic mechanics question


PD wrote:
> jgreenfield@xxxxxxxxxxx wrote:
> > PD wrote:
> > > jgreenfield@xxxxxxxxxxx wrote:
> > > > vsgdp wrote:
> > > > > Hi,
> > > > >
> > > > > Suppose gravity does not exist.
> > > > >
> > > > > A car is traving on a frictionless horizontal plane to the right at some
> > > > > velocity v.
> > > > >
> > > > > Up ahead there is a ramp (no gravity).
> > > > >
> > > > > When the car hits the ramp, is it correct to say that some of the velocity
> > > > > is lost due to the impulse. And the remaining velocity is the projection of
> > > > > v onto the tangent vector of the ramp?
> > > >
> > > >
> > > > Newton: "Energy is neither created nor destroyed, but may change from
> > > > one form to another". So the car alters its direction (and so does the
> > > > ramp minisculely), loses linear speed (gives up kinetic energy) and
> > > > heat is "generated"/shared between the ramp and car from the "lost" KE.
> > > >
> > > > Now think on to the "adding velocities under SR rules".
> > > > Using the adopted method of SR, the CHANGES in DIRECTION of the objects
> > > > whose velocities are to be added, and the inherent transfers of energy
> > > > therein as visualised in this thought experiment, are IGNORED.
> > > > Such "ignorance" falsifies the theory, as the method of addition which
> > > > underlies it is bogus.
> > > >
> > >
> > > And this is crap.
> > > 1. Relativistic addition of velocity in more than 1 dimension is
> > > perfectly well-defined, though you may not have seen that.
> >
> > Correct! All I see is the King's hairy arse; no magic cloak.
> > I am of course referring to additions of velocities for objects on the
> > x axis
> > (a car firing a bullet ahead). SR addition blythely introduces a
> > "slope" for the path of the bullet, totally ignoring the energy needed
> > to produce the change in direction.
>
> What slope would that be? Citation please. I believe you are
> misunderstanding whatever you are reading. Ah, wait, let me guess.
> You're looking at the slope of a worldline on an x vs t graph? And you
> can't distinguish the physical meaning of that from an x vs y graph?

Yes. I am looking at a slope which has another triangle placed upon it,
which viewed in its own frame, would still have its base on the x axis,
NOT transposed to (rotated) lie on the "slope". To plot velocity, which
is ALREADY a function of time, against another "axis" of time, leaves
situation of plotting time against itself, which may be ok for the
gullible. Of course, Srists think it ok, as they apriori equip
different objects with clocks which tick at a rate which protects "The
Theory", and the two "times" being different, accept the graph as seen.
>
> >
> > > 2. Conservation of momentum is not tantamount to a velocity addition.
> >
> > A convenient cop out (re-definition) to protect SR
>
> Bull. A baseball is pitched toward homeplate at 90 mph. The batter
> swings forward, the end of the bat moving at 60 mph just before
> contact. After contact, the bat continues forward at 59 mph, and the
> baseball heads toward the outfield at 209 mph. All this is completely
> consistent with conservation of momentum. Where is the velocity
> addition here?

This may be fine for low speed, but SR says if the bat is travelling at
relatavistic speed, and the ball also, then the combined (added) speed
is less (.5c +.5c = <c)
Given perfect elasticity (no heat exchanges), whence the lost
momentum???????
>
> >
> > > 3. Conservation of momentum (including collisions in more than one
> > > dimension) is strictly enforced in special relativity.
> >
> > With distances per time that alter magically depending on the speed of
> > the object, how could it fail?
>
> Failure to understand SR and conservation of momentum, and subsequent
> of same as "magic", is not a valid critique.

c = fu
when f changes, or u changes, WHY SHOULD the other alter to maintain c
the same??????????
THAT is MAGIC

Jim G
c'=c+v

.

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