Experiment5

00:13:17
https://www.youtube.com/watch?v=NO9X6yac8g0

Resumo

TLDREn aquesta sessió, es discuteixen les lleis de Newton, centrant-se en la tensió i la força de fregament. La primera llei estableix que un objecte en moviment es manté en moviment a menys que una força externa actuï sobre ell. La segona llei relaciona la força neta amb el canvi de moment, mentre que la tercera llei afirma que per cada acció hi ha una reacció igual i oposada. S'exploren experiments per mesurar la tensió en cordes i l'impacte de la fregament en l'acceleració d'un carro. Els resultats mostren que la fregament redueix l'acceleració i que la tensió és constant en una corda massless.

Conclusões

  • 🔍 Revisió de les lleis de Newton
  • ⚖️ Primera llei: moviment uniforme
  • 📈 Segona llei: força i canvi de moment
  • 🔄 Tercera llei: acció i reacció
  • 🧪 Equipament necessari per a experiments
  • 📊 Mesura de la tensió en cordes
  • 📉 Efecte de la fregament en l'acceleració
  • ⚙️ Comparació de tensió en moviment i estacionari
  • 📉 Fregament redueix l'acceleració
  • 🔧 Importància de la calibració dels instruments

Linha do tempo

  • 00:00:00 - 00:05:00

    En aquesta sessió, es revisen les tres lleis de Newton. La primera llei estableix que un cos en moviment uniforme es manté en moviment i un cos en repòs es manté en repòs si la força total que actua sobre ell és zero. La segona llei indica que si la força total no és zero, la quantitat de moviment d'un objecte canvia amb el temps, i la tercera llei parla de l'acció i reacció, on les forces són iguals en magnitud però oposades en direcció. Es presenten els materials necessaris per a l'experimentació, incloent un detector de moviment i probes de força.

  • 00:05:00 - 00:13:17

    L'activitat 1 explora la tensió i la llei de Newton. S'utilitzen dues probes de força connectades amb una goma elàstica per mesurar les forces en direccions oposades, demostrant que són iguals en magnitud. En les activitats següents, es mesura la tensió en un cordó fixat a un carro, mostrant que la tensió és constant i independent de la longitud del cordó. Finalment, es discuteix l'impacte de la fricció en el moviment del carro, comparant les dades amb i sense fricció, i com això afecta l'acceleració segons la segona llei de Newton.

Mapa mental

Vídeo de perguntas e respostas

  • Quines són les tres lleis de Newton?

    La primera llei tracta sobre el moviment uniforme i l'estat de repòs, la segona llei relaciona la força amb el canvi de moment, i la tercera llei parla d'acció i reacció.

  • Quin equipament es necessita per a l'experiment?

    Es necessita un detector de moviment, probes de força, una corda, bandes de goma i masses.

  • Com es mesura la tensió en una corda?

    Es connecten dues probes de força amb una corda i es tira d'elles per mesurar la força.

  • Quin efecte té la fregament en l'acceleració?

    La fregament redueix l'acceleració del carro, ja que disminueix la força neta que actua sobre ell.

  • Què passa amb la tensió quan el carro està en moviment?

    La tensió és menor quan el carro es mou en comparació amb quan està estacionari.

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Rolagem automática:
  • 00:00:01
    uh hi today i'll be explaining lap five
  • 00:00:04
    called tension and friction force
  • 00:00:07
    uh i just uh really quickly review trini
  • 00:00:10
    autonomous dog
  • 00:00:12
    the first newton law is about when a
  • 00:00:14
    body is in
  • 00:00:15
    a uniform motion remains in uniform
  • 00:00:18
    and a body at rest remains at rest
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    if the total force acting on the object
  • 00:00:26
    is zero so
  • 00:00:31
    the total force is zero and
  • 00:00:35
    there is no acceleration so it means
  • 00:00:37
    that b
  • 00:00:38
    is constant uh newton's second law
  • 00:00:42
    uh when there is is about uh
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    when the total force acting on the
  • 00:00:47
    object is not
  • 00:00:48
    zero so in this case in case the
  • 00:00:51
    momentum of the
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    object is change will change with time
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    uh so it means that the total force
  • 00:00:58
    acting on the object is equal to delta p
  • 00:01:02
    change of momentum width and time and
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    you know that momentum
  • 00:01:06
    is a mass of the object times velocity
  • 00:01:10
    momentum is a vector quantity because
  • 00:01:12
    velocity is a vector quantity
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    and because mass here is constant you
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    have mass times delta v divided by
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    delta t and you know that delta v
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    divided by delta t
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    is acceleration and newton's third law
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    is about
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    action and reaction it means that if uh
  • 00:01:30
    object a
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    exert force on object b object b also
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    exerts force on object a these forces
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    are equal in magnitude
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    but opposite in direction so
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    the force the magnitude of force exerted
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    an object
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    a is equal to the magnitude of the force
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    exerted on
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    object b but they
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    are in the opposite direction
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    and they don't cancel each other because
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    they are extended on different objects
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    the equipment that you need for today is
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    a
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    force probe i'm sorry a motion detector
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    and a track one card
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    a friction pad which will be attached to
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    the cart but we don't need it now
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    to first probe and uh please check the
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    fourth probe
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    if they are not calibrated they don't
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    show
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    they are not close to zero you need to
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    calibrate them
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    if necessary if not just keep going
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    and you need strings a few rubber bands
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    and some masses
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    so first investigation was
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    one is about tension and newton's third
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    law
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    so for activity one you need
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    two force probes and connect
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    these two force probe with a rubber band
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    and
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    pull them away from each other and at
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    the same time
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    take data so i as usual i click on call
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    it
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    and i apply force on the
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    fourth probes or move them away from
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    each other and you can
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    sorry i do it one more time
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    okay so uh you can see that the forces
  • 00:03:38
    here
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    are equal in magnitude
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    but opposite in direction one of them is
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    positive the other one is
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    negative but they are similar to each
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    other if you see that the magnitude
  • 00:03:51
    if you notice that the magnitudes are a
  • 00:03:54
    little different it means that one of
  • 00:03:56
    the fourth probe maybe is not calibrated
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    very well
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    but the magnet should be the same and
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    the opposite is
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    the sign
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    that you can see the board later
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    okay so this was about action and
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    reaction you took third law
  • 00:04:16
    um activity one two is about
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    uh tension uh so you need
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    to fix one of the force proof in order
  • 00:04:27
    to do
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    that just tilt this
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    pulley and
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    fix one of the force probes to this rod
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    and hold the other fourth row uh you
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    need to
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    stream with two different lenses
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    so connect the two fourth probes
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    with a string and
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    pull one of them to the away from the
  • 00:05:02
    other force group and at the same time
  • 00:05:04
    take data
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    here you can see tension on
  • 00:05:16
    uh two end of the string and if the
  • 00:05:19
    string
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    is stationary or massless you can see
  • 00:05:22
    that the tension along the string is
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    the same everywhere and along the string
  • 00:05:28
    is the same everywhere and
  • 00:05:29
    it propagates undiminished and so
  • 00:05:33
    as you can see tension is uh the same on
  • 00:05:36
    both
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    force probes so they have the same
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    magnitude but opposite direction
  • 00:05:42
    and after that i
  • 00:05:45
    take the shorter string and do the same
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    thing and i
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    just want to investigate whether the
  • 00:05:51
    length of this require changing the
  • 00:05:52
    length of this tree
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    tension will change or not
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    so we'll start click on correct and
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    the same
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    we can see they are completely similar
  • 00:06:09
    to
  • 00:06:09
    each other they have the same magnet
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    so this is activity uh one two
  • 00:06:17
    and activity one 3
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    just
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    tilt the pulley back because we need it
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    attach one of the force probe uh
  • 00:06:36
    drops to the cart
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    and
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    another one
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    to the end of the string and pass the
  • 00:06:51
    string over the pulley
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    and hold it only the stationary they
  • 00:07:07
    don't need to move
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    and take date
  • 00:07:18
    so again you are measuring the
  • 00:07:22
    force exerted on the fourth probe which
  • 00:07:24
    is tension here
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    on both ends of the string and they are
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    the same
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    constant they are not changing same
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    attitude
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    and that's activity one three
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    inactive in activity one four
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    uh uh one of the fourth probe was that
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    is attached to the card and we replaced
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    the second
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    fourth rope with the 200 grams
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    mass and
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    just pull the horse probe
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    and cart and start to take data click on
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    collect
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    hold it for one second and after that
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    let it go and stop taking data so
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    when you hold it stationary um there is
  • 00:08:14
    tension
  • 00:08:14
    but there is no acceleration so if you
  • 00:08:17
    write down a neutrons first now
  • 00:08:19
    for the
  • 00:08:24
    uh hanging mass 200 grams
  • 00:08:27
    you can see that there is gravitational
  • 00:08:30
    force
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    downward and tension so
  • 00:08:35
    oven and you hold it stationary there is
  • 00:08:37
    no acceleration so it means that the
  • 00:08:40
    total force x acting on the
  • 00:08:43
    mass is zero so it means that
  • 00:08:46
    tension here is equal to the
  • 00:08:51
    weight of the mass but
  • 00:08:55
    when you release it it will start to
  • 00:08:58
    speed up
  • 00:08:59
    so in this case
  • 00:09:04
    it is moving the mass is moving in this
  • 00:09:07
    direction
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    so and it has accelerate acceleration
  • 00:09:12
    so if we have fg we have tension
  • 00:09:15
    uh we call this ts
  • 00:09:18
    it means that tension when the cart is
  • 00:09:21
    stationary
  • 00:09:22
    and tm means tension when the cart is
  • 00:09:26
    moving
  • 00:09:27
    so if you write down newton's second now
  • 00:09:29
    and the total force is equal to mass of
  • 00:09:32
    the object times acceleration
  • 00:09:34
    so here f g minus t m
  • 00:09:37
    is equal to m a so from here
  • 00:09:40
    t m is equal to f g minus
  • 00:09:44
    m a so if you compare these two tension
  • 00:09:47
    tension event and the chord is
  • 00:09:49
    stationary uh we can
  • 00:09:51
    when um tension when the card is moving
  • 00:09:53
    you can see that
  • 00:09:54
    uh tension um and ts is larger that t
  • 00:09:59
    m um so um you can see it under
  • 00:10:02
    your graph as well uh that's
  • 00:10:05
    for activity um yeah so from your graph
  • 00:10:09
    you are supposed to
  • 00:10:10
    please use examine and read the tension
  • 00:10:14
    write down the tension
  • 00:10:15
    uh when the card is stationary and the
  • 00:10:17
    tension when the card is
  • 00:10:19
    moving and also acceleration
  • 00:10:21
    acceleration when the card was
  • 00:10:30
    moving
  • 00:10:34
    uh this is about activity one four
  • 00:10:36
    investigation
  • 00:10:38
    uh investigative investigation two is
  • 00:10:40
    about the friction force and we want to
  • 00:10:42
    investigate
  • 00:10:43
    how uh friction force effect the motion
  • 00:10:46
    of the card
  • 00:10:47
    and how does it affect them and use on
  • 00:10:49
    second law
  • 00:10:50
    uh so at first the card
  • 00:10:53
    release the card um and take data
  • 00:10:58
    so it start to speed up so and
  • 00:11:01
    there is no friction because i raise the
  • 00:11:04
    friction pad
  • 00:11:05
    so start at the same time start to click
  • 00:11:08
    date
  • 00:11:12
    in the second case i just lowered the
  • 00:11:15
    friction pad
  • 00:11:20
    make sure that it is touching the track
  • 00:11:22
    so there is a
  • 00:11:23
    now there is friction between the cart
  • 00:11:25
    and the track due to the friction path
  • 00:11:28
    and i do the same thing release it and
  • 00:11:30
    take data at the same time
  • 00:11:36
    okay now uh you can
  • 00:11:40
    see on your graph you have a force
  • 00:11:42
    versus time
  • 00:11:43
    and acceleration on versus time
  • 00:11:46
    here you can see that in both cases the
  • 00:11:48
    applied force that which is the tension
  • 00:11:51
    is the same it's not changing with
  • 00:11:53
    friction
  • 00:11:54
    but acceleration um are different
  • 00:11:58
    so you can see then there is friction
  • 00:12:00
    acceleration is smaller
  • 00:12:01
    uh so um from a second news on second
  • 00:12:05
    law you know that
  • 00:12:06
    the total force acting on the object is
  • 00:12:09
    acts equal to acceleration
  • 00:12:11
    so when there is a friction total force
  • 00:12:14
    is
  • 00:12:14
    smaller it means that you should
  • 00:12:16
    consider it in the newton's second law
  • 00:12:18
    so it is um changing the acceleration
  • 00:12:21
    and that's
  • 00:12:24
    uh here we have a demo for output
  • 00:12:26
    machine as you can see we have two
  • 00:12:27
    masses
  • 00:12:28
    um which are connected by a string one
  • 00:12:31
    of them is much heavier than the other
  • 00:12:33
    one
  • 00:12:33
    so if i release them it will
  • 00:12:36
    drop down uh pulling the other one up
  • 00:12:39
    um there is a small friction here but if
  • 00:12:42
    i
  • 00:12:43
    add um two more if i add two more
  • 00:12:46
    turns here i can adjust the friction
  • 00:12:51
    so by increasing the friction
  • 00:12:54
    according to newton's seconds law i can
  • 00:12:58
    change the total force acting on the
  • 00:13:00
    object so making the total force
  • 00:13:03
    zero and so the acceleration zero
  • 00:13:06
    so the if i release them and they won't
  • 00:13:09
    move so it means that a friction is
  • 00:13:11
    important and we should consider it in
  • 00:13:12
    newton's second law
  • 00:13:14
    and it can change the acceleration
Etiquetas
  • Newton
  • tensió
  • fregament
  • forces
  • experiments
  • acceleration
  • mòbil
  • probes de força
  • masses
  • dinàmica