From Newsgroup: sci.physics.research

My animation
https://www.geogebra.org/classic/g8jc28u2
is a 2-pan scales.

If you press "Start," obviously nothing moves, because the two weights
are equal and neither weight has more weight than the other.

However, if you increase the mass of body B from 1 to 2 kg (by clicking
on the appropriate box), when you press "Start," the plates accelerate.

The second plate descends because the force F2 of body 2 on its plate is greater than the reaction F3 of the plate on body 2, and the first plate ascends because the force F4 of its plate on body 1 is greater than the reaction F1 of body 1 on the plate.

Keep in mind that the force F4 = +19.6N is nothing other than the force
F2 = -19.6N changed in sign because it was transferred by the
constraints from one plate to the other, and the force F3 = +9.8N is
nothing other than the force F1 = -9.8N changed in sign because it was transferred from one side to the other.

This is all an experiment (and not an abstract theory) and demonstrates
that action does not equal reaction.

Therefore, the third law is wrong.

Can anyone dispute the correctness of this proof?

Luigi Fortunati

[[Mod. note --
The author has described an example of Atwood's machine, <https://en.wikipedia.org/wiki/Atwood_machine>
-- jt]]
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From Newsgroup: sci.physics.research

In article <<10to3ep$3sr9b$1@dont-email.me>, Luigi Fortunati wrote

My animation
https://www.geogebra.org/classic/g8jc28u2
is a 2-pan scales.

If you press "Start," obviously nothing moves, because the two weights
are equal and neither weight has more weight than the other.

However, if you increase the mass of body B from 1 to 2 kg (by clicking
on the appropriate box), when you press "Start," the plates accelerate.

The second plate descends because the force F2 of body 2 on its plate is greater than the reaction F3 of the plate on body 2, and the first plate ascends because the force F4 of its plate on body 1 is greater than the reaction F1 of body 1 on the plate.

Keep in mind that the force F4 = +19.6N is nothing other than the force
F2 = -19.6N changed in sign because it was transferred by the
constraints from one plate to the other, and the force F3 = +9.8N is
nothing other than the force F1 = -9.8N changed in sign because it was transferred from one side to the other.

The problem here is the assumption that F1 (the force A exerts on its
balance pan) = -9.8N and F2 (the force B exerts on its balance pan)
= -19.6N. That would be true (given mA = 1kg and mB = 2kg, and assuming
the lab is an inertial reference frame on the Earth's surface) *if* A
and B were unaccelerated.

But here A and B are accelerating (vertically), so F1 will differ from
-9.8N and F2 will differ from -19.6N.
--
-- "Jonathan Thornburg [remove -color to reply]" <dr.j.thornburg@gmail-pink.com>
(he/him; on the west coast of Canada)
"Totalitarianism in power invariably replaces all first-rate talents,
regardless of their sympathies, with those crackpots and fools whose
lack of intelligence and creativity is still the best guarantee of
their loyalty." -- Hannah Arendt, "The Origins of Totalitarianism"
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From Newsgroup: sci.physics.research

Il 11/05/2026 07:07, Jonathan Thornburg [remove -color to reply] <dr.j.thornburg@gmail-pink.com> ha scritto:

In article <<10to3ep$3sr9b$1@dont-email.me>, Luigi Fortunati wrote

My animation
https://www.geogebra.org/classic/g8jc28u2
is a 2-pan scales.

If you press "Start," obviously nothing moves, because the two weights
are equal and neither weight has more weight than the other.

However, if you increase the mass of body B from 1 to 2 kg (by clicking
on the appropriate box), when you press "Start," the plates accelerate.

The second plate descends because the force F2 of body 2 on its plate is
greater than the reaction F3 of the plate on body 2, and the first plate
ascends because the force F4 of its plate on body 1 is greater than the
reaction F1 of body 1 on the plate.

Keep in mind that the force F4 = +19.6N is nothing other than the force
F2 = -19.6N changed in sign because it was transferred by the
constraints from one plate to the other, and the force F3 = +9.8N is
nothing other than the force F1 = -9.8N changed in sign because it was
transferred from one side to the other.

The problem here is the assumption that F1 (the force A exerts on its
balance pan) = -9.8N and F2 (the force B exerts on its balance pan)
= -19.6N. That would be true (given mA = 1kg and mB = 2kg, and assuming
the lab is an inertial reference frame on the Earth's surface) *if* A
and B were unaccelerated.

But here A and B are accelerating (vertically), so F1 will differ from
-9.8N and F2 will differ from -19.6N.

I wrote that F1 is the force-weight mg=-9.8N of body A on the plate, and
you say it's something else.

Okay.

And how much is this "something else"?

And what is the force-weight F2=mg of body B if it's not -19.6N?

Luigi
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