The Trick that Makes Understanding Physics as Simple as Drawing a Picture: Physics Help Room

Ғылым және технология

F = ma can be really hard to solve, so it's important to be able to get intuition about a physics system without having to solve F = ma. The trick is to think about the potential energy curve. Get the notes for free here: courses.physicswithelliot.com...
Get the NOTES, the PROBLEM SHEET, the SOLUTIONS, and the ANIMATIONS: www.physicswithelliot.com/pot...
Tutoring inquiries: www.physicswithelliot.com/tut...
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me! You can make a recurring contribution at / physicswithelliot , or make a one time contribution at www.physicswithelliot.com/sup.... Thank you so much!
About physics help room videos:
These are intro-level physics videos aimed at students taking their first physics classes. In each video, I'll teach you the fundamentals of a particular physics topic you're likely to meet in your first classes on mechanics and electromagnetism.
About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at www.physicswithelliot.com.

Пікірлер: 118

  • @olivierrokks
    @olivierrokks2 жыл бұрын

    Bruhhhh, Video, Notes AND Homework??? I love you.

  • @EnemyOfEldar
    @EnemyOfEldar2 жыл бұрын

    Dude I got my degree (Msci) in Theoretical Physics 5 years ago and I have been a maths/physics educator since. You're awesome. Keep doing what you're doing. You've just levelled up my teaching for sure and it will make a difference to my students as well. Godspeed, Elliot.

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    So glad to hear it!

  • @juanpablomartinez1671
    @juanpablomartinez16712 жыл бұрын

    I've just met your channel and it's terrifically awesome. The way which you explain is superb, the focus of the content it's original and very sharp. I really like it. Thank you so much!

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thank you so much Juan!

  • @mohammedal-haddad2652
    @mohammedal-haddad26522 жыл бұрын

    This is exacly the introductory classical mechanics lectures that I always wanted to find to develope the necessary background to learn quantum mechanics. Thank you very much.

  • @adamfattal468

    @adamfattal468

    Жыл бұрын

    Tekram

  • @douglasstrother6584
    @douglasstrother65842 жыл бұрын

    Nice! Developing a physical understanding of what a solution should look like using this technique and other graphical approaches is a critical skill. There are about six core problems which can be solved in closed-form; that's one reason why the simple harmonic oscillator is used everywhere! It's amusing that the pendulum can't be solved in closed-form. (The period as a function of angle can be expressed in terms of elliptic integrals.) The three-body problem is also fundamentally intractable. This presentation hints at the concept of Phase Space which is used in Classical, Statistical and Quantum Mechanics.

  • @channelsixtysix066
    @channelsixtysix0662 жыл бұрын

    Just found this channel and subscribed. I have subscribed to several maths channels and I'd like to subscribe to more physics channels. Great presentation, Elliot, thank you.

  • @TheAgentJesus
    @TheAgentJesus2 жыл бұрын

    Dude you are awesome, this is such quality content and exactly the kind of thing I love seeing more of in the educative sphere of KZread! Thank you so much; do you have a patreon or anything like that?

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thank you so much! And thank you for asking; creating a Patreon has been on my to do list, and I've just now gone ahead and set it up at Patreon.com/physicswithelliot. Thank you in advance if you decide to be my first patron!! Please also let me know about what other topics you'd be interested in learning about

  • @TheAgentJesus

    @TheAgentJesus

    2 жыл бұрын

    @@PhysicswithElliot unfortunately I'm a bit strapped at the moment - indeed, I've had to suspend the two or three patreon accounts I'm normally subscribed to; that said, as soon as I'm financially stable again I'll be sure to replace one of them (which is a great channel, but already has plenty of crowd-funding attention and hardly needs my help) with yours so as to hopefully help you with those initial hurdles: you definitely deserve it! I particularly like that you make a point of including problem sets; it's habits like that which could really turn KZread into more than just "Edutainment," but an actual functional supplement to (or even eventual 'replacement' of) traditional secondary education. So seriously, thanks so much for your effort! Hopefully by the time I come back in a month or so to subscribe I'll find that I'm not the first!

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Not to worry!

  • @jjzh
    @jjzh2 жыл бұрын

    Hey Elliot, your channel is one of the best physics related channels I've ever come across: very simple and simultaneously esthetically beautiful design, with insightful information, props for the great work. I'm currently taking a course on quantum mechanics and I loved the way how you linked Poisson brackets with the commutators and it really helped my deepen my understanding of the subject. I'd love to see some more videos on quantum mechanics that help us develop an intuition for the way it works (e.g. quantum tunneling etc.)

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks JK! More quantum mechanics videos to come!

  • @hubertorhant8884
    @hubertorhant8884 Жыл бұрын

    spoken on a soft tone and calmness takes away the "anxiety" brought by the differential equation so that one can focus on the subject at matter ! i've seen this potential graphing many times but any of my teachers dared to emphasize the R_min and R_max meaning and the impact on the orbit ! Just brilliant ! makes me wanna go back to U again. Awesome Elliot ;-)

  • @aleksandr_berdnikov
    @aleksandr_berdnikov2 жыл бұрын

    A trick that I found incredibly useful for puzzles of the type "which direction will it move" (like a spool with a thread pulled at an angle, or a bike with someone on the ground pushing its pedal, or with "faster than wind" sailing cars, etc.) However complex it is, the stuff when acted upon will change its motion so as to accommodate your efforts (the thread of spool should be pulled towards your pull, not pull you hand out; the bikes movement should let your push on the pedal succeed, not push you with the pedal instead; the car will, given no friction, speed up as long as it makes the blades planes move less relative to the air; etc)

  • @whilewecan
    @whilewecan Жыл бұрын

    Thank you!!! This is the first time I encountered with such perspective. Revelation. Impressive.

  • @longyang-funvideo
    @longyang-funvideo Жыл бұрын

    You are the best among youtuber for physics stuff! Watching your videos is a joy!

  • @wisnuape
    @wisnuape2 жыл бұрын

    Great content packed with deep physical insight. Now i learn much more about potential energy. Thanks !

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Wisnu!

  • @robertcantwell9569
    @robertcantwell95692 жыл бұрын

    Exceptional presentation , thank you for ur time and effort .

  • @charleshudson5330
    @charleshudson53302 жыл бұрын

    Excellent video. Wonderful channel. You have the most perfect baritone for narration. Silky smooth; smoothly reassuring. A tone that can be trusted. (A young Morgan Freeman.)

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Ha! Thanks Charles!

  • @Woodpecker_18
    @Woodpecker_182 жыл бұрын

    KZread recommended your channel and I am amazed by the explanation, thanks buddy.

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Glad I could help!

  • @Noah_Krakatoa
    @Noah_Krakatoa10 ай бұрын

    Great video! For some reason, I like thinking of elliptical orbits sort of like a juggler throwing balls up in the air, where the aphelion would be at the top of the page and the star and perihelion would be at the bottom. So instead of a planet going round and round it’s going up and under

  • @flix7280
    @flix72802 жыл бұрын

    your channel is freaking awesome prof!

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Ayush!

  • @RahulSingh-ry9ht
    @RahulSingh-ry9ht Жыл бұрын

    Found you yesterday, amazing stuff...!

  • @lucksterduck
    @lucksterduck2 жыл бұрын

    Such a wonderful video. Thank you!

  • @aleksandr_berdnikov
    @aleksandr_berdnikov2 жыл бұрын

    I also like how the effective potential (or ang.momentum & energy invariants) make easy work of geodesics on surfaces of revolution building nice intuition for their features

  • @david50665
    @david506652 жыл бұрын

    even all the notes in the link!!!...wow this guy is really on top of it...

  • @esquire9445
    @esquire94458 ай бұрын

    This was awesome, seriously gifted teacher. Wow.

  • @kammuller6620
    @kammuller6620 Жыл бұрын

    I really enjoyed the video. It was fun and very relaxing to watch. I will recommend it to my students.

  • @PhysicswithElliot

    @PhysicswithElliot

    Жыл бұрын

    Thanks Kam!

  • @joselemgruber8098
    @joselemgruber80982 жыл бұрын

    Very good !! Thanks for all !

  • @albertdowson5436
    @albertdowson54362 жыл бұрын

    Thank you so much bro , the explanation was awesome , really enjoyed the entire video

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Albert!

  • @JoseAntonio-ml8yg
    @JoseAntonio-ml8yg Жыл бұрын

    Your videos are extremely helpfull. Thanks a lot!

  • @leonardopavan2013
    @leonardopavan20132 жыл бұрын

    Man, you're just amazing. I'm your biggest fan from Brazil!!

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Leonardo!

  • @JeanDAVID
    @JeanDAVID11 ай бұрын

    This new concept of the effective potential energy is astonishing to describe the motion of a celestial body around another massive one !

  • @AndrewPa
    @AndrewPa2 жыл бұрын

    iMPRESSIVE - as professional in subject would like to say good job mate!

  • @3koningen
    @3koningen Жыл бұрын

    Thank you. You really help!

  • @Jello1963
    @Jello19632 жыл бұрын

    Could you explain Lagrange points as well with potential energy?

  • @mionio1977
    @mionio19772 жыл бұрын

    Great job !!! Keep on !!!

  • @brendanward2991
    @brendanward29912 жыл бұрын

    20:00 - the graph seems to imply that the orbital speed is at a maximum not at perihelion but just before and just after perihelion, when U(eff) is at a minimum.

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    The potential energy goes like -1/r, so it gets more and more negative as r gets smaller. Then since the total energy K + U is a constant, you make the kinetic energy biggest by making r as small as it can go. Remember that the effective potential isn't just the gravitational potential -1/r, but also includes the L^2/r^2 term that came from the angular kinetic energy of the full 2d problem

  • @MrShenCat
    @MrShenCat2 жыл бұрын

    Does this trick come from any papers ? It's intuitive. I wonder if their conjugate variables (ie moment vs time diagram) have similar patterns.

  • @federicopinto9353
    @federicopinto93532 жыл бұрын

    This is great!

  • @ravikantpatil3398
    @ravikantpatil33983 ай бұрын

    Great explained thanx

  • @ib2415
    @ib24152 жыл бұрын

    Very illuminating

  • @robertdavie1221
    @robertdavie1221 Жыл бұрын

    Great explanation!

  • @declanwk1
    @declanwk12 жыл бұрын

    very interesting and enlightening

  • @mesbahalsarraj399
    @mesbahalsarraj3992 жыл бұрын

    Great channel! Keep it up. Excellent audio and video quality. Which camera do you use BTW?

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    iPhone!

  • @TIO540S1
    @TIO540S12 жыл бұрын

    Might I suggest a video on another topic that yields qualitative and, in some cases, quantitative information about a system without solving the differential equations of motion. That is dimensional analysis and the Buckingham Pi Theorem.

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Will definitely make a dimensional analysis video before too long!

  • @ilteriskagan7305
    @ilteriskagan73056 ай бұрын

    How and where do you do these type of simulations. Please explain. Can we do it too?

  • @jackflash8756
    @jackflash87564 ай бұрын

    Really excellent video.

  • @tomctutor
    @tomctutor2 жыл бұрын

    Very good Elliot! I feel it prudent to outline some terminology that often confuses students.. The Field is (by definition) _= - the gradient of the Potential_ . *g= - ∇V.* here g is not energy it is a specific force. Ex. it may be the electrostatic force per unit charge at a point [N/C in S.I units]. The potential V is also not an energy (it is the specific potential energy). In our electrostatics example V would be U/Q [J/C or volt]. Consider gravitation, g = Force per unit mass [N/Kg] which of course is simply acceleration from F=ma. The Gravitational Potential Energy at that point would be U= Vm. I hope that clears up any confusion about what is meant by scalar potentials and vector fields versus Potential Energy. ☺ ← ◎

  • @masganteng1987
    @masganteng19872 жыл бұрын

    genius. thanks very much

  • @barak363363
    @barak36336319 күн бұрын

    Great channel!

  • @kushagrasinha4828
    @kushagrasinha4828 Жыл бұрын

    Thank you 💗💗💗💗😊 brother I understood everything ❤️🔥❤️

  • @neillinneball

    @neillinneball

    Жыл бұрын

    Outstanding!the best I have ever seen. Keep up these great explanations.

  • @amarnathck574
    @amarnathck5742 жыл бұрын

    Question, someone help. If effective potential at r min and r max are the same, and E is constant, then doesn’t that mean that KE is also the same at r min and r max since KE= E-p(eff)??

  • @MrPoornakumar
    @MrPoornakumar Жыл бұрын

    Thank you, very much.

  • @katnisseverdeen5466
    @katnisseverdeen5466 Жыл бұрын

    I'm 16 and in my first year of A-levels. This all seems fascinating and well-explained, but just slightly out of reach with the schooling I have. Can anyone recommend any resources just one step below this? Thanks!

  • @abhisheknath5723
    @abhisheknath57232 жыл бұрын

    I know your channel is going to grow a lot... I am glad to be one of the early one (well not so early)

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Abhishek!

  • @sibilakshman9575
    @sibilakshman95756 ай бұрын

    The derivative of Veff , if 0 would imply that the orbit is circular , can you explain why?

  • @ElFazo
    @ElFazo10 ай бұрын

    very cool thanks

  • @wavvyair
    @wavvyair2 ай бұрын

    Awesome video

  • @chrisr9320
    @chrisr93202 жыл бұрын

    great content!

  • @finaltheorygames1781
    @finaltheorygames178110 ай бұрын

    I liked the picture of the potential energy and the orbit of the planet, its shows a whole other perspective.

  • @eulersfollower7140
    @eulersfollower71402 жыл бұрын

    Hey I have a question if you don't mind .In the case of circular orbit ,even if the Kinetic Energy is zero ,it moves because it has angular velocity & angular momentum if I am not mistaken ,in the case of elliptical orbits it has some Kinetic energy (ie) it's not zero except at r_min & r_max .How does that translational Kinetic Energy play in the context of elliptical orbits ? A great video ,please consider making courses on various topics .

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    The kinetic energy has a radial piece and an angular piece. It's never zero because the planet always at least has an angular velocity. The effective potential, meanwhile, is a trick that lets us use angular momentum conservation to group the angular kinetic energy term together with the ordinary potential energy for the purposes of analyzing the motion

  • @eulersfollower7140

    @eulersfollower7140

    2 жыл бұрын

    @@PhysicswithElliot I am still having a problem considering the effective potential in the diagram instead of ordinary potential ,i don't understand how they are equivalent ,could you explain this part ? Thank you ,have a nice day.

  • @sergiolucas38
    @sergiolucas382 жыл бұрын

    great video, thanks :)

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Thanks Sergio!

  • @ninja-nd1wm
    @ninja-nd1wm Жыл бұрын

    Uh sir can you please tell me about the PARABOLA case ? That's what I am usually confused about What is the difference between the hyperbola and the parabola orbits?

  • @keppa3635
    @keppa36352 жыл бұрын

    Hey buddy can u plz make a video on writing a lagrange for two block spring system on frictionless surface plzzz...

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    Set up your coordinates, write down the kinetic energy of each block, and write the potential energy stored in the spring. Then take the difference and you're home free!

  • @atticusfinch3991
    @atticusfinch3991 Жыл бұрын

    Thanks

  • @bowlampar
    @bowlampar2 жыл бұрын

    Somehow both Physics and Drawing are not simple subjects, they can hardly ' short cut 'to become 'simple' . Student still need to do his homework and read up regularly.😁

  • @whatitmeans
    @whatitmeans2 жыл бұрын

    Under which assumptions the relation dU/dt=F stands?... Could you made a video showing how it will be applyied for the nonlinear damped pendulum? Or energy losses will crash the method?

  • @PhysicswithElliot

    @PhysicswithElliot

    2 жыл бұрын

    You mean F = dp/dt? Or -dU/dx?

  • @tomctutor

    @tomctutor

    2 жыл бұрын

    Force is indeed F= dp/dt in any context. This is another definition just stating that 1 [N] is equivalent to 1 [kgm/s^2] in SI units.

  • @sciencedon3993
    @sciencedon39932 жыл бұрын

    wonderful

  • @kanshokmituithung2782
    @kanshokmituithung2782 Жыл бұрын

    May you live long!

  • @charlesbromberick4247
    @charlesbromberick42472 жыл бұрын

    I thought uou were going to mention CONSERVATION OF ENERGY or ENERGY CONSIDERATIONS, like George Jaun of Cal Tech would do.

  • @aibisxLife
    @aibisxLife4 ай бұрын

    Nice💫

  • @jukukalle100
    @jukukalle1005 ай бұрын

    I know it’s an older video, but just wanted to let you know that the potential energy U for pendulum in the 2nd example is wrong. You took L cos θ as the height component, when actually it should be L - L cosθ = L (1 - cos θ). so U = mgL(1 - cosθ). The graph is also wrong because of it. At θ = 0 potential energy U has to be 0 for a pendulum. Your graph crosses U axis at -mgL but it should be at 0. Though the following qualitative analysis isn’t affected by this error Otherwise thank you for the great video!

  • @MarcoAGJ
    @MarcoAGJ2 жыл бұрын

    Interesting.

  • @bangbang1108
    @bangbang1108 Жыл бұрын

    wow your channel is fukin top g. really incredible

  • @jaysmith12
    @jaysmith122 жыл бұрын

    I don't think your wavefunction at 7:50 is correct but I hate to ruin the video. We are measuring phase space of a simple pendulum and separatix math within hamiltonian mechanics reflects the real function of this operation. Making full cyclical rotations is a wave function of pi radians along a periodic timeline. Surely a pendulum makes a spiral function around the stable point.

  • @dcode1000
    @dcode10002 жыл бұрын

    More please. And just a suggestion: if could focus more on visually explaining physics concepts using high quality animation visuals like bluebrown that would make the videos even 10x better.

  • @tomctutor

    @tomctutor

    2 жыл бұрын

    And probably 10X work for poor Eliot, I like his coloured pen sketches, cheap and chearful and leave 3B1B for the sexy animations. ✎

  • @user-cm6hv6tw4m
    @user-cm6hv6tw4m3 ай бұрын

    at 11.54 u really start to find the purpose of watching this video

  • @bscutajar
    @bscutajar Жыл бұрын

    14:21 is wrong, it depicts the force of gravity to be outwards due to the negative sign

  • @davidbrisbane7206
    @davidbrisbane7206 Жыл бұрын

    _The motion of the Earth around a star like the Sun_ ... as if the Earth could orbit any other star 😂🤣.

  • @SSNewberry
    @SSNewberry2 жыл бұрын

    use the Lagrangian

  • @tomctutor

    @tomctutor

    2 жыл бұрын

    Lagrangian (E-U) is equivalent to classical mechanics (E+U) so no need

  • @davidbrisbane7206
    @davidbrisbane7206 Жыл бұрын

    The only tool you need is Wolfram Alpha 😀.

  • @grantofat6438
    @grantofat64389 ай бұрын

    The sad thing is that it is not simple to draw a picture. Most people can't do that.

  • @schmetterling4477

    @schmetterling4477

    3 ай бұрын

    That's why you just have to keep at it. You will get better in time and the images in your mind and on the white boards will help you to deepen your understanding quickly. Physics is an extremely visual science. Physicists scribble and draw stuff all day long. It really helps. Don't be shy about it.

  • @wdobni
    @wdobni2 жыл бұрын

    these are fun little math games if your mind runs in a mathematical direction....clearly you have a friendly familiar conversational aquaintance with mathematics.....so smoke em if you got em....but i fail to see the point of anybody studying introductory or undergraduate physics - they will never be doing any CERN research or designing any xray machines or hydrogen bombs if one is going to become a professional engineer then this stuff has relevance.....but for most university students learning an FFT and how to apply the newtonian or the lagrangian will be about as useful in later life as chinese poetry or gender theory i don't think there is any useful 'trick' to learning physics and calculus, most of it comes from repetition and problem solving exercises, and eventually the more gifted develop what you are calling an 'intuition' but its actually a familiarity gained by exposure....a concert pianist does not develop a trick or intuition about Mozart, he/she gets there by the method of 8000 hours of practise the same is true for physics and the maths, they are not intuitive disciplines, any moreso than russian is an intuitive language or organic chemistry is an intuitive approach to benzene based aromatic hydrocarbons...its all labor, repetition, and practise.....viewed through the retrospectoscope 10 years later the cancer surgeon might remark that most cancer surgery is 'intuitive' but that is only because he/she eats. sleeps, talks, dreams, and reads only cancer surgery.

  • @tomctutor

    @tomctutor

    2 жыл бұрын

    All that said, reminds me of the story about Einstein whom failed his maths class miserably in Junior school, his schoolmaster stated on his report; "Young Albert wont amount to anything academically and recommend he takes up some hand skill instead". Mastering maths at this level takes a lot of work and study so don't give up if you are really interested in the subject.✍

  • @davidrandell2224
    @davidrandell22242 жыл бұрын

    Galilean relative motion has the earth approaching the released object. D=1/2 at^2 main part of proper equation. The earth is expanding at 16 feet per second per second constant acceleration: gravity. “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon.

  • @davidbrisbane7206
    @davidbrisbane7206 Жыл бұрын

    Wow ... but gravity is not a force 😂🤣😂😂🤣

  • @vg6761
    @vg67612 жыл бұрын

    Let's be honest. We're never gonna understand this shit. Don't even waste your time. 😅

  • @orglancs
    @orglancs2 жыл бұрын

    To someone like me, whose love of science was destroyed by school teachers, this is sheer click-bait. I was lost by 2:50 and stopped the video. The trick, if there is one, is invisible and you'll have to be a lot more understanding of people like me (and there are lots of us) if you want to make physics accessible to us. Anything with an equation in it has had it as far as I am concerned. How do I know you are not cheating, shunting your symbols round like chessmen on a board instead of real things? What would your equations look like, if you actually replaced your symbols by real numbers? Would they add up? There's no way of knowing, is there, because you keep everything concealed behind abstract symbols.

  • @98danielray

    @98danielray

    2 жыл бұрын

    what the fuck are you even trying to say? of course the equations work if you replace things. thats how equations work

  • @vg6761

    @vg6761

    2 жыл бұрын

    Ikr fuck western 'physics'

  • @tomctutor

    @tomctutor

    2 жыл бұрын

    Dear friend.... You cant have physics without maths, same as you cant have fish without chips. Nature, although elusive in most of its behavior, reveals itself sometimes in symmetry and beautiful logic. Maths is the language in which we interpret and analyze its form. Just like English is how you enjoy a Shakespearian play. Whatever way you crack it open, you need the power and formalism of maths to fully understand it. Any equation in physics is an expression of some "physical law" as Finemann would often state. E.g. force is proportional to acceleration and the amount of matter in a body, so F=ma a.k.a. Newtons' Law of Motion. I think you misunderstand maths equations and their application in our world. The symbolic sophestry is unfortunately necessary so go learn.

  • @sadececns00
    @sadececns006 ай бұрын

    Awesome!!!

  • @abdirazaqali8921
    @abdirazaqali8921 Жыл бұрын

    Please share us your email. You are great physicist.

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