• The "net" force

    From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Sat Mar 22 16:31:37 2025
    From Newsgroup: sci.physics.research

    In the animation https://www.geogebra.org/classic/sr8fxezb there is the
    force F of the hand that pushes the point A of the car.

    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.

    But is the force F that pushes the point A of the car also a "net"
    force?

    Luigi Fortunati
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  • From Mikko@mikko.levanto@iki.fi to sci.physics.research on Sun Mar 23 12:44:06 2025
    From Newsgroup: sci.physics.research

    On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:

    In the animation https://www.geogebra.org/classic/sr8fxezb there is the
    force F of the hand that pushes the point A of the car.
    =20
    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.
    =20
    But is the force F that pushes the point A of the car also a "net"
    force?

    A net force to the car is not a net force to a part of the car.
    A part of a car has inteactions with other parts of the car. In addition, gravity affects the part and the ground under the car touches or does
    not touch the part.

    --=20
    Mikko
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  • From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Mon Mar 24 08:19:19 2025
    From Newsgroup: sci.physics.research

    Mikko il 23/03/2025 06:44:06 ha scritto:
    On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:

    In the animation https://www.geogebra.org/classic/sr8fxezb there is the
    force F of the hand that pushes the point A of the car.
    =20
    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.
    =20
    But is the force F that pushes the point A of the car also a "net"
    force?

    A net force to the car is not a net force to a part of the car.

    I agree: the force F of the hand is a net force on the car but it is not a net force on point A.

    Consequentially, on point A there must be *also* a force acting contrary to the force F.

    So, does the blue reaction contrary force FR of my animation act only on the hand that pushes (as you all keep saying) or does it act *also* on point A of the car?

    Luigi
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  • From Mikko@mikko.levanto@iki.fi to sci.physics.research on Mon Mar 24 09:14:22 2025
    From Newsgroup: sci.physics.research

    On 2025-03-24 08:19:19 +0000, Luigi Fortunati said:

    Mikko il 23/03/2025 06:44:06 ha scritto:
    On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:

    In the animation https://www.geogebra.org/classic/sr8fxezb there is the
    force F of the hand that pushes the point A of the car.
    =20
    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.
    =20
    But is the force F that pushes the point A of the car also a "net"
    force?

    A net force to the car is not a net force to a part of the car.

    I agree: the force F of the hand is a net force on the car but it is
    not a net force on point A.

    Consequentially, on point A there must be *also* a force acting
    contrary to the force F.

    So, does the blue reaction contrary force FR of my animation act only
    on the hand that pushes (as you all keep saying) or does it act *also*
    on point A of the car?

    The interactions are between material parts. A point does not interact.
    --
    Mikko

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  • From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Tue Mar 25 21:19:14 2025
    From Newsgroup: sci.physics.research

    Mikko il 24/03/2025 10:14:22 ha scritto:
    On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:
    =20
    In the animation https://www.geogebra.org/classic/sr8fxezb there is =
    the
    force F of the hand that pushes the point A of the car.
    =3D20
    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.
    =3D20
    But is the force F that pushes the point A of the car also a "net"
    force?
    =20
    A net force to the car is not a net force to a part of the car.
    =20
    I agree: the force F of the hand is a net force on the car but it is=20
    not a net force on point A.
    =20
    Consequentially, on point A there must be *also* a force acting=20
    contrary to the force F.
    =20
    So, does the blue reaction contrary force FR of my animation act only=20
    on the hand that pushes (as you all keep saying) or does it act *also*=
    =20
    on point A of the car?

    The interactions are between material parts. A point does not interact.

    I am referring to the material point, that is, the particle.
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  • From Luigi Fortunati@fortunati.luigi@gmail.com to sci.physics.research on Tue Mar 25 21:22:41 2025
    From Newsgroup: sci.physics.research

    Mikko il 24/03/2025 10:14:22 ha scritto:
    On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:

    In the animation https://www.geogebra.org/classic/sr8fxezb there is =
    the
    force F of the hand that pushes the point A of the car.

    The force F that pushes the car is certainly a "net" force because
    there is no one to push the car from the other side.

    But is the force F that pushes the point A of the car also a "net"
    force?

    A net force to the car is not a net force to a part of the car.

    I agree: the force F of the hand is a net force on the car but it is
    not a net force on point A.

    Consequentially, on point A there must be *also* a force acting
    contrary to the force F.

    So, does the blue reaction contrary force FR of my animation act only
    on the hand that pushes (as you all keep saying) or does it act *also*=

    on point A of the car?

    The interactions are between material parts. A point does not interact.

    I am referring to the material point, that is, the particle.

    Particle A of the machine, in addition to receiving the black force F
    of the hand, does it or does it not receive the blue reaction force FR
    of my animation?

    Luigi

    [[Mod. note -- No, it doesn't: the reaction force FR (shown in blue)
    acts on the hand, whereas particle A is part of the car.

    I should also point out one important error in the diagram: the diagram
    shows FR as different in magnitude (arrow of length 2) from F (arrow of
    length 3). Newton's 3rd law says that FR has the same magnitude as F,
    so these two arrows should be shown as the same length.
    -- jt]]
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