Julius Sumner Miller Lesson 4: Newton's Third Law of Motion - Momentum

00:14:30
https://www.youtube.com/watch?v=TyvX4-Ouovg

Summary

TLDRLa vidéo présentée par Juliia Suna Miller se concentre sur la troisième loi du mouvement de Newton, laquelle stipule que toute action entraîne une réaction égale et opposée. Miller explique cette loi à travers plusieurs expériences simples, comme le lancement d'un ballon, les interactions entre deux voitures de masses différentes reliées par un ressort, et le fonctionnement de gadgets et jouets, comme les hélicoptères à ressort et les engins moteurs de Héros. Miller souligne que la conservation de la quantité de mouvement est centrale dans ces démonstrations, où l'impulsion d'un objet est transférée à un autre. En démontrant ces principes avec des objets du quotidien et des outils de physique classiques, Miller rend ces concepts accessibles et divertissants, tout en posant des questions stimulantes sur les phénomènes physiques impliqués, comme la formation de givre lors de la libération rapide d'un gaz.

Takeaways

  • 🛠️ Newton et ses lois sont essentiels à la physique.
  • 🎈 Les ballons et fusées illustrent l'action-réaction.
  • 🚗 La démonstration avec deux voitures explique la relation entre masse et accélération.
  • 💨 Les cartouches de CO2 montrent la conservation de la quantité de mouvement.
  • ⚙️ Les moteurs de Héros affichent clairement les principes des lois de Newton.
  • 📐 La conservation de la quantité de mouvement est démontrée dans plusieurs perspectives.
  • 🔭 Les jouets sont des outils puissants pour comprendre la physique.
  • 🔊 La vitesse du son dans l'acier est rapide, créant des démonstrations fascinantes.
  • ❄️ Les effets du gaz sur la température incluent questions de physique
  • 🧸 Les démonstrations avec des jouets rendent la physique ludique et éducative.

Timeline

  • 00:00:00 - 00:14:30

    Le segment suivant inclut des démonstrations supplémentaires, montrant des sphères en acier démontrant la conservation de quantités de mouvement lors des collisions. L'impulsion transmise est égale avant et après l'impact. Elle utilise un modèle de jouet comme 'Hero's engine' pour montrer la réaction chimique et la conservation de mouvement. Enfin, elle résume les trois lois de Newton, avec une démonstration finale utilisant une plateforme à roulettes pour illustrer comment le déplacement d'un côté entraîne un mouvement opposé, soulignant encore l'action et la réaction.

Mind Map

Mind Map

Frequently Asked Question

  • Qu'est-ce que la troisième loi du mouvement de Newton ?

    Pour chaque action, il y a une réaction égale et opposée.

  • Comment est illustrée la troisième loi de Newton avec des jouets dans la vidéo ?

    Un jouet ballon propulsé par de l'air s'échappant démontre cette loi, car le ballon se déplace dans la direction opposée au flux d'air.

  • La présence d'une atmosphère est-elle nécessaire pour qu'une fusée fonctionne ?

    Non, une fusée fonctionne mieux dans le vide car elle n'a pas besoin de l'atmosphère pour se propulser.

  • Comment les deux voitures démontrent-elles la troisième loi ?

    En tirant une voiture lourde et une voiture légère avec un ressort, la voiture légère accélère plus vite, mais les forces restent égales et opposées.

  • Pourquoi le gaz dans une cartouche de CO2 fait-il bouger le véhicule dans la direction opposée ?

    Le gaz s'échappant a une masse et une vitesse créant une quantité de mouvement qui propulse le véhicule dans la direction inverse.

  • Comment fonctionnent les "Engine de Héros" ?

    Une boîte de conserve avec des tuyaux recourbés libère de la vapeur, faisant tourner la boîte autour d'un axe en raison de la loi d'action-réaction de Newton.

  • Pourquoi retire-t-il sa main rapidement lors des collisions des sphères en acier ?

    Les sphères réagissent rapidement avec la vitesse du son dans l'acier, rendant la démonstration impressionnante.

  • Quels sont les exemples de conservation de la quantité de mouvement montrés dans la vidéo ?

    L'exemple des voitures, des cartouches de CO2 et des moteurs de vapeur montrent comment la quantité de mouvement se conserve après une interaction.

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  • 00:00:00
    [Music]
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    how do you do ladies and gentlemen and
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    boys and girls I am juliia Suna Miller
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    and physics is my business and our
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    business today is the very special third
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    law in Newton's three laws of
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    motion and to view it at least once in
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    our lifetime in the Latin I have it here
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    Lex three oxion contrarium
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    simpal
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    reion now if you didn't know any Latin
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    at all You' see something in there about
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    action and reaction and indeed that's
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    what it sums up to be third law to every
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    action there is always an equal and
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    opposite a contrary reaction or
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    the mutual actions of any two bodies are
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    always equal and oppositely
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    directed now a strange introduction to
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    this law would be as follows consider me
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    standing still and quiet on the earth
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    and I jump up in this
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    manner I ask did you feel the Earth
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    recoil and the answer is it must be it
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    did indeed recoil even though though you
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    may not have felt it why here is the
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    earth enormous Mass here I am a teeny
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    wey creature of little Mass I push down
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    on the floor and with a force F which
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    acts on me and on the earth and as
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    before in the second law my little Mass
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    you detect has an enormous acceleration
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    up I go but the Earth having an enormous
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    Mass has a teeny wiy acceleration
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    which you cannot
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    detect
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    so
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    consider Newton's third law in a toy
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    here is a little vehicle with some
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    Wheels to which is fixed a rubber
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    balloon and I blow some air in the
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    balloon now I'm going to let the air
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    come out of a certain hole orifice here
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    the air comes out this way and what must
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    the vehicle do the vehicle must go the
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    other way watch it
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    there it goes and so I am reminded of a
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    certain exercise that goes like this
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    here is a rocket vehicle we have some
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    stuff in here in a state of
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    combustion the products of the
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    combustion come out here millions of
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    little particles of stuff now many
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    people have the distorted notion that
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    this stuff coming out here must push
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    against the atmosphere in order for this
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    to go
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    and I say that is utterly erroneous this
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    system this vehicle works better where
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    there is nothing because we want the
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    little mass of stuff coming out there to
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    come out with the greatest possible
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    velocity and hence have the greatest
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    rate of change of momentum the product
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    of M and V being
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    momentum now I'm going to go back to the
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    two cars because the case of the two
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    cars I said earlier very important
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    important massive car less massive car I
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    stretched the spring between them one in
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    the same Force acts on both and we
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    witness an astonishing thing here is the
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    massive car here is the little car less
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    inertia there is the spring now what did
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    we see the same Force acted on both but
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    you notice
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    notice that the smaller one had the
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    bigger acceler
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    ation and the bigger one had the Lesser
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    acceleration and therefore in the same
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    time of travel and they would both
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    travel the same time from Time Zero to
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    the time of collision clearly the
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    smaller one has the higher velocity so
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    writing the momentum of both cars we
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    would equate it as follows the large car
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    has a little velocity the little car an
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    enormous velocity and these momenta are
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    equal very important that you see that
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    point that the same Force acts on both
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    the accelerations are inversely as the
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    masses and the momenta are equal in
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    another program I will talk about their
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    energies and we will discover a very
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    strange thing now more on this
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    conservation of momentum which is
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    essentially Newton's third law here I
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    have a CO2 cartridge gas in here under
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    enormous pressure here is a carriage in
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    which I put
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    it I'll look around that end and you
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    will notice that there is a barrier on
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    this end of the cartridge of the
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    carriage now what am I going to do I am
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    going to make a hole in this end of the
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    cartridge the gases come out this way oh
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    I erased that before the gases come out
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    out this way and they have a certain
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    momentum their mass and their velocity
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    the vehicle must go the other way watch
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    it now
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    watch there it goes there it
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    goes Miller's Earthbound rocket now a
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    very oh very important thing it fled
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    away fled away momentum I'm sure I would
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    have asked a question had I had it in
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    hand and question I would feel it to be
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    very cold very cold and I want to know
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    why is it cold a second question there
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    could indeed be frost on it and the
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    question is where cometh the frost in
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    the first question we have a very
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    powerful piece of
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    physics the gas is coming out must do
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    work this costs energy and I leave it
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    there for further discussion in another
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    program now let's go to something still
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    more dramatic again conservation of
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    linear
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    momentum here is an array of Steel
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    spheres highly elastic steel is highly
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    elastic by that I mean when they are
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    deformed they
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    recover they lie in the lowest potential
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    configuration I take one up the plane
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    let it go having given it some potential
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    energy and it collides with the system
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    at rest and watch what happens on the
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    remote
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    end
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    one oh that's terrific watch it look
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    it nearly
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    instantaneously indeed I'm led to ask
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    how fast does the impulse get down there
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    answer with the same velocity as the
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    velocity of sound in steel which is
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    about 15,000 ft per second so if this
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    were a foot long or that's more likely a
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    foot long that's 9 12 in watch
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    it 115,000 of a second you notice too
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    that the whole system experiences some
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    motion that's because they all wish to
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    seek a lower potential
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    plane now one at Collision MV one goes
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    away MV watch two two MV plus MV two MV
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    now let us disregard the intermediate or
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    the other motions that we witness
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    because a discussion of this would
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    divert me from my purpose here all I
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    wish to say is that whatever the
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    momentum before the Collision so that is
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    the momentum after one
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    one
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    two
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    two three oh notice they are seeking a
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    lower potential plane the energy of a
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    system runs
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    downhill free oh that's pretty notice
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    they are seeking a lower potential plane
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    four watch it now notice they are
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    seeking a lower potential plane just as
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    my energy is running downhill now as I
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    do the
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    show
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    four five
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    up five and so we say without question
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    the momentum before the Collision is
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    equal to the momentum
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    after consider another classical
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    demonstration of mine which is easy to
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    do and quite dramatic here is a steel
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    pipe this demonstration I will call
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    virtual v i r
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    t there are some demonstrations that I
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    do for real and I call them real
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    demonstrations this one we will imagine
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    an imagination is a very necessary
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    ingredient of this business we will
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    imagine a steel pipe closed up tightly
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    on one end with a cap mounted on Wheels
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    and in this chamber I put some dry ice
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    solid
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    CO2 then with a wooden plug I plug it up
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    very firmly very firmly and I let it
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    stand here on the table in the hot air
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    of the classroom or the TV studio and
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    what happens the CO2 sublimes goes into
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    gas or vapor the pressure builds up more
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    and more the pressure gets enormous
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    inside something has to go what goes the
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    cap with an enormous velocity enough
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    indeed to kill a man so if you should do
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    this I warn you have some caution and
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    what happens to the vehicle it goes the
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    other way big Mass little velocity
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    little Mass large velocity conservation
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    of linear
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    momentum powerful business powerful
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    consider toys have a large role in my
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    business because the physics of toys is
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    an enchanting thing to engage in toys I
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    would have you understand ladies and
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    gentlemen and boys and girls toys are
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    intended for child's play but the
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    physics of them is hardly that here is a
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    little propeller with some uh
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    inclined blades and I have mounted
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    it in a chamber wherein resides a
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    spring so I am storing some wound up
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    elastic energy in the spring and I
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    release it I did that one prematurely
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    what happens how is Newton's third
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    law how does it play a role here
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    answer the pitch blade engages the air
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    dry waves the air down with a momentum
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    MV the vehicle must go up watch it there
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    it is oh that's a pretty thing and then
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    it's spinning as a top about which I
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    will speak in another program so the
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    question to be asked is how does a bird
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    fly here is a bird flying here is a bird
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    I'm probably viewed as a vulture bird
  • 00:11:54
    bird I can only fly if I push the air
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    down down and that's why I go up now
  • 00:12:02
    when a bird Soares as they do ever so
  • 00:12:05
    gracefully that is quite another thing
  • 00:12:08
    again to be considered
  • 00:12:10
    subsequently or a balloon here's a
  • 00:12:16
    balloon incidentally I'm going to do a
  • 00:12:19
    program on bubbles and the like and I
  • 00:12:23
    will raise the question of why is it
  • 00:12:25
    hardest to blow up a balloon at the very
  • 00:12:27
    beginning and easiest to blow it up the
  • 00:12:30
    bigger you get it but anyway I've put
  • 00:12:32
    some air in there now you know if I let
  • 00:12:34
    the air out here momentum MV momentum
  • 00:12:37
    the other way there is like that and one
  • 00:12:40
    last
  • 00:12:42
    exploration one last
  • 00:12:44
    exploration Hero's
  • 00:12:46
    engine here is a little vehicle you can
  • 00:12:49
    make out of a tin can you put some tubes
  • 00:12:52
    through it and bend the tubes at right
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    angles to their uh lengths put put some
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    water in
  • 00:13:00
    here boil the water the steam more
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    exactly Vapor which becomes Steam on
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    condensation The Vapor comes out the
  • 00:13:10
    orifices and this turns around ever so
  • 00:13:14
    fast this is a substantial demonstration
  • 00:13:17
    of Newton's third law and here is a
  • 00:13:20
    bigger scale one on which we could run a
  • 00:13:24
    very quantitative experiment so much
  • 00:13:26
    water so much heat energy put in so so
  • 00:13:29
    much energy gotten in the angular
  • 00:13:31
    velocity of the
  • 00:13:33
    vehicle and
  • 00:13:36
    so what must we now say we have
  • 00:13:41
    explored in the passing shows the first
  • 00:13:44
    law in two parts the second law which is
  • 00:13:47
    wrapped up in fals Ma and the third law
  • 00:13:51
    referred to as action and reaction which
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    I will close in this way here is a very
  • 00:14:00
    freewheeling
  • 00:14:02
    vehicle and you know that if I stand on
  • 00:14:06
    it at rest and go forward the cart must
  • 00:14:10
    go
  • 00:14:11
    backward which it does and I say that
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    when I Walk This Way the earth goes the
  • 00:14:17
    other way I thank you for your attention
  • 00:14:22
    [Music]
Tags
  • Newton
  • troisième loi
  • action-réaction
  • physique
  • expériences
  • quantité de mouvement
  • conservation
  • éducation
  • jouets
  • démonstrations