Re: Conservation of angular momentum

On Jun 5, 9:52 am, Peter <Poakfi...@xxxxxxx> wrote:
On Jun 4, 6:31 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:





On Jun 4, 5:16 pm, Peter <Poakfi...@xxxxxxx> wrote:

On Jun 4, 2:16 pm, "Greg Neill" <gneill...@xxxxxxxxxxxxxxx> wrote:

"Peter" <Poakfi...@xxxxxxx> wrote in message

news:1180979218.846926.157070@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Velocity is a vector (rectilinear).Angular(circular) is curvilinear.
One cannot have an object in rectilinear and circular motion at the
same time.

You never took physics.

One body passing by another and traveling in a
perfectly straight line hasangularmomentum
with respect to the other. Why? Because the
"look" angle from one to the other is rotating
around an axis.

I know they teach that any object in rectilinear motion hasangular
momentumrelative to some point of reference. This means it can have
as many differentangularmomenta as one chooses. Do you really think
this is meaningful, correct, or useful?

Yes, it does, and yes it is. An object's linearmomentumalso depends
on the point of reference. As an example, ask yourself what your
linearmomentumis right now, as you sit there.

The laws of physics do not demand that there be a unique value
associated withmomentumorangularmomentum, only that once a
reference point is chosen, then the laws (for example,conservationofmomentum) hold.

PD-

In a given inertial reference frame,

Precisely.

And with respect to a given reference point, the angular momentum of
an object is unique. All objects with the same mass and the same cross-
product of radius and velocity have the same "angular momentum".

the momentum of an object is
unique. All objects with the same mass and velocity have the same
momentum. Not so for "angular momentum." Two objects with the same
mass and velocity can have different "angular momentum." That is dumb,
ridiculous, and makes no sense. Don't you think so?

Not at all.
You feel free to restrict the uniqueness of momentum to a given
inertial reference frame, but you feel restricting the uniqueness of
angular momentum to a given reference point to be dumb, ridiculous,
and makes no sense. Why you would think so is beyond me.

PD

.

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