From Newsgroup: sci.physics.research

In the animation of Newton's pendulum
https://www.geogebra.org/classic/pwvqwpme
there is the first sphere that hits point A of sphere 2, on which it
exerts its action F1.

Does this red force F1 stop at point A or does it continue undisturbed
through the bodies of spheres 2, 3 and 4, up to point B of sphere 5,
where it arrives with almost unchanged intensity, as seen in the
animation?

Luigi Fortunati


[[Mod. note -- Forces never "stop" at a point. The actual mechanics
are a bit more complicated -- see
https://en.wikipedia.org/wiki/Newton%27s_cradle
for a nice discussion.
-- jt]]
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From Newsgroup: sci.physics.research

On 2025-10-11 17:15:48 +0000, Luigi Fortunati said:

In the animation of Newton's pendulum https://www.geogebra.org/classic/pwvqwpme
there is the first sphere that hits point A of sphere 2, on which it
exerts its action F1.

Does this red force F1 stop at point A or does it continue undisturbed through the bodies of spheres 2, 3 and 4, up to point B of sphere 5,
where it arrives with almost unchanged intensity, as seen in the
animation?

Neither, really. Of course you can always say that the force F1 stop
at A and after that it is another force. But that other force is a
continuation of the force F1 and is there only because the forst F1
was at A. But because all effects of the force F1 don't arrive to
other points at the same time the force at other points is not the
same.

[[Mod. note -- Forces never "stop" at a point. The actual mechanics
are a bit more complicated -- see
https://en.wikipedia.org/wiki/Newton%27s_cradle
for a nice discussion.
-- jt]]

The moderaton's note is correct.
--
Mikko
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From Newsgroup: sci.physics.research

On Sun, 12 Oct 2025 11:37:46 PDT, Mikko <mikko.levanto@iki.fi> wrote:

On 2025-10-11 17:15:48 +0000, Luigi Fortunati said:

In the animation of Newton's pendulum
https://www.geogebra.org/classic/pwvqwpme
there is the first sphere that hits point A of sphere 2, on which it
exerts its action F1.

Does this red force F1 stop at point A or does it continue undisturbed
through the bodies of spheres 2, 3 and 4, up to point B of sphere 5,
where it arrives with almost unchanged intensity, as seen in the
animation?

Neither, really. Of course you can always say that the force F1 stop
at A and after that it is another force. But that other force is a >continuation of the force F1 and is there only because the forst F1
was at A. But because all effects of the force F1 don't arrive to
other points at the same time the force at other points is not the
same.

[[Mod. note -- Forces never "stop" at a point. The actual mechanics
are a bit more complicated -- see
https://en.wikipedia.org/wiki/Newton%27s_cradle
for a nice discussion.
-- jt]]

The moderaton's note is correct.

https://en.wikipedia.org/wiki/Newton%27s_cradle says: "When one sphere
at the end is lifted and released, it strikes the stationary spheres, compressing them and thereby transmitting a pressure wave through the stationary spheres, which creates a force that pushes the last sphere
upward. The last sphere swings back and strikes the stationary
spheres, repeating the effect in the opposite direction".

All this means that the impact of the first sphere on the second
generates a pressure which, in the horizontal direction, creates two
opposing forces.

One is the one directed backwards, which stops sphere 1 and ends
there.

Instead, the other force (F1) is propagated forward by the pressure
wave through the stationary spheres 2,3 and 4, up to sphere 5, on
which it discharges as the wave does when it arrives on the beach.

The task of the waves is precisely this: to transmit the impulse
forward.

In this case, the impulse is the force F1.

Luigi Fortunati
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From Newsgroup: sci.physics.research

On 2025-10-13 11:45:00 +0000, Luigi Fortunati said:

On Sun, 12 Oct 2025 11:37:46 PDT, Mikko <mikko.levanto@iki.fi> wrote:
=20

On 2025-10-11 17:15:48 +0000, Luigi Fortunati said:

In the animation of Newton's pendulum
https://www.geogebra.org/classic/pwvqwpme
there is the first sphere that hits point A of sphere 2, on which it
exerts its action F1.
=20
Does this red force F1 stop at point A or does it continue undisturbe=

d

through the bodies of spheres 2, 3 and 4, up to point B of sphere 5,
where it arrives with almost unchanged intensity, as seen in the
animation?

=20
Neither, really. Of course you can always say that the force F1 stop
at A and after that it is another force. But that other force is a
continuation of the force F1 and is there only because the forst F1
was at A. But because all effects of the force F1 don't arrive to
other points at the same time the force at other points is not the
same.
=20

[[Mod. note -- Forces never "stop" at a point. The actual mechanics
are a bit more complicated -- see
https://en.wikipedia.org/wiki/Newton%27s_cradle
for a nice discussion.
-- jt]]

=20
The moderaton's note is correct.

=20
https://en.wikipedia.org/wiki/Newton%27s_cradle says: "When one sphere
at the end is lifted and released, it strikes the stationary spheres, compressing them and thereby transmitting a pressure wave through the stationary spheres, which creates a force that pushes the last sphere
upward. The last sphere swings back and strikes the stationary
spheres, repeating the effect in the opposite direction".

Note that a wave from a small source (the first impact) sperad in all directions. In this case the wave reflects from the suface of the first
shere and a large part of it arrives to the contact of spheres 1 and 2
withing suffient short time to contribute to the impulse given to the
second sphere. A part of the wave misses the contact with ephere 2
and all the time the wave is attena=C3=BAated by the internal friction. Therefore force in each contact is smallter than in the previous contact
and the motion gradually slows down.

--=20
Mikko
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From Newsgroup: sci.physics.research

Mikko <mikko.levanto@iki.fi> wrote:

Note that a wave from a small source (the first impact) sperad in all directions. In this case the wave reflects from the suface of the first
shere and a large part of it arrives to the contact of spheres 1 and 2 withing suffient short time to contribute to the impulse given to the
second sphere. A part of the wave misses the contact with ephere 2
and all the time the wave is attena=C3=BAated by the internal friction. Therefore force in each contact is smallter than in the previous contact
and the motion gradually slows down.

I'm not sure the shape of the balls is critical to focusing the wave.
It should work as long as the balls are made of an extremely stiff
material.

A small fraction of the impulse is *not* transmitted all the way
to the end ball. The rest gets spread among the other balls and
they eventually oscillate together as a group (before the oscillations
die out).
--
pa at panix dot com
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