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  • Live Action and Reaction

    From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Mon Jun 8 00:26:20 2026
    From Newsgroup: sci.physics.research

    From: SMTP%"fortunati.luigi@gmail.com" 7-JUN-2026 11:24:59.39
    To: sci-physics-research@moderators.isc.org
    CC:
    Subj: Live Action and Reaction

    In the diagram
    https://www.geogebra.org/classic/narsb96a
    there is an inclined plane where body A pushes my hands downward with
    force F1=-100N (action) and my hands respond with force F2=+100N
    (reaction), so everything remains stationary.

    The force F1 does not vary over time.

    However, the force F2 changes every time I choose to increase or
    decrease it.

    It is my will that decides how and when to react to external action.

    And not the third law.

    And what happens when, suddenly, I decide to double my reaction F2 from
    +100N to +200N?

    Luigi

    [[Mod. note --
    The statement "The force F1 does not vary over time." isn't true:
    if body A and your hand are accelerating, then F1 varies with the
    acceleration.

    As an extreme example, if you accelerate your hand down the inclied plane
    at the same acceleration that body A would free-fall in the absence
    of any forces fro the hand (this acceleration = g * sin(alpha), where
    alpha is the plane's inclination angle), then the force F1 will be
    *zero*.

    And if you accelerate your hand down the inclined plane even faster
    than that, the body A won't be able to keep up with your hand, so they
    won't stay in contact and again the force F1 will be *zero*.
    -- jt]]
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  • From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Thu Jun 11 08:35:11 2026
    From Newsgroup: sci.physics.research

    Il 08/06/2026 09:26, Luigi Fortunati ha scritto:
    From: SMTP%"fortunati.luigi@gmail.com" 7-JUN-2026 11:24:59.39
    To: sci-physics-research@moderators.isc.org
    CC:
    Subj: Live Action and Reaction

    In the diagram
    https://www.geogebra.org/classic/narsb96a
    there is an inclined plane where body A pushes my hands downward with
    force F1=-100N (action) and my hands respond with force F2=+100N
    (reaction), so everything remains stationary.

    The force F1 does not vary over time.

    However, the force F2 changes every time I choose to increase or
    decrease it.

    It is my will that decides how and when to react to external action.

    And not the third law.

    And what happens when, suddenly, I decide to double my reaction F2 from
    +100N to +200N?

    Luigi

    [[Mod. note --
    The statement "The force F1 does not vary over time." isn't true:
    if body A and your hand are accelerating, then F1 varies with the acceleration.

    The statement "The force F1 does not vary with time" refers to the scheme https://www.geogebra.org/classic/narsb96a
    where there is no acceleration.

    Body A would like to move downward, but the force F2 prevents it, and
    body A remains stationary.

    My hands would like to move upward, but the force F1 prevents it, and
    the hands remain stationary.

    The forces are there, but they don't accelerate anything because they
    are opposing forces: F1 opposes F2, and F2 opposes F1.

    There are no net forces.

    And how can we move from this system to one where there are net forces?

    There's only one way to do it: one of the two forces F1 and F2 must
    prevail, because as long as they are equal, there are no net forces, and
    no acceleration either.

    But F1 alone cannot change, and only F2 can: that's why I wrote that the
    force F1 does not change.

    Are there other ways to create a net force where there aren't any net
    forces?

    Luigi
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