1. Radiation History to the Present - Understanding the Discovery of the Neutron

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  • เผยแพร่เมื่อ 25 มิ.ย. 2024
  • MIT 22.01 Introduction to Nuclear Engineering and Ionizing Radiation, Fall 2016
    Instructor: Michael Short
    View the complete course: ocw.mit.edu/22-01F16
    TH-cam Playlist: • MIT 22.01 Introduction...
    A brief summary of the discovery of forms of ionizing radiation up to the 1932 discovery of the neutron. We introduce mass-energy equivalence for the first time and explain how these cutting-edge experiments (for their time) conclusively proved the existence of high-energy, ionizing radiation.
    License: Creative Commons BY-NC-SA
    More information at ocw.mit.edu/terms
    More courses at ocw.mit.edu

ความคิดเห็น • 289

  • @mitocw
    @mitocw  3 ปีที่แล้ว +30

    To report potential content errors, please use this form: forms.gle/8B2zcUvfCtgJdTdE7

    • @sbunyusuny1298
      @sbunyusuny1298 ปีที่แล้ว +2

      我怕你抄我逼样,you better know trump 146+

    • @sbunyusuny1298
      @sbunyusuny1298 ปีที่แล้ว

      BE THANKFUL 你还有屁股

    • @sbunyusuny1298
      @sbunyusuny1298 ปีที่แล้ว

      columbia好转学,2011 off

    • @sbunyusuny1298
      @sbunyusuny1298 ปีที่แล้ว

      islamic 2121

    • @sbunyusuny1298
      @sbunyusuny1298 ปีที่แล้ว

      nth wrong on the western FRONT, WARTIME

  • @erikaenander5374
    @erikaenander5374 3 หลายเดือนก่อน +17

    I was a professor for over 15 years, and I cannot express how much I appreciate this professors teaching, personality, and frankly how he just seems like a good person. In my experience, the quality of a class cannot rest on a professor’s, attitude alone, but without enthusiasm for his subject, his students, and where he’s teaching, the subject matter doesn’t matter. You have to teach students first. You don’t teach science. you teach science students. This guy is great!!

  • @maxpaju
    @maxpaju 3 ปีที่แล้ว +171

    This teacher is great. He's got technical depth but he's also a great communicator, which he stresses to the students how important it is.

  • @rossboyer2764
    @rossboyer2764 4 ปีที่แล้ว +410

    Love that you guys make stuff like this publicly available!

    • @NazriB
      @NazriB 2 ปีที่แล้ว

      Lies again? Hello RHQ

  • @LinusE
    @LinusE 2 ปีที่แล้ว +78

    This teacher really is a great example of what a university lecturer should be. Clears out how the rest of the semester ties in with the current lesson etc, what questions will be answered, clears out that the class don't need to know all this from the get-go. Really great, instead of just shoving information and tells the students to solve it themselves

    • @maijaclarke9790
      @maijaclarke9790 ปีที่แล้ว +1

      I agree. He introduces us to topics we know of but not deeper - causes, the danger, the time it may last , the chemistry of the various danger toxic chemicals so we can make sensible opinions of how safe such reactions are and Whether we can forgo that process even if it seems great. After all the remains of radioactive materials will remain some for hundreds of years but the reaction towers begin to lose their strength some 40 to 60 hrs and need to be replaced!

  • @mgmartin51
    @mgmartin51 4 ปีที่แล้ว +340

    This fellow is an engaging teacher. I wish I were taking his class. Wait- I can!

    • @ricardobautista-garcia8492
      @ricardobautista-garcia8492 4 ปีที่แล้ว +14

      @Chad Thaddeus Hello fellow classmate

    • @benkleschinsky
      @benkleschinsky 3 ปีที่แล้ว +18

      I had a high school GPA of 2.5 and I'm taking an MIT course, lol!

    • @benkleschinsky
      @benkleschinsky 3 ปีที่แล้ว +24

      The biggest downfall of general public education is that most schools discourage working together as cheating. When in the scientific community and real world, debate and collaboration are essential to making new discoveries.

    • @MSDOS128
      @MSDOS128 2 ปีที่แล้ว +1

      @@benkleschinsky exactly, and even if someone helps you to understand a topic, it's usually someone considered smart among your peers, not necessarily a person who can explain it better than a smart student or a teacher.

    • @benkleschinsky
      @benkleschinsky 2 ปีที่แล้ว +6

      @@MSDOS128 The ironic twist is that some of the most brilliant people make terrible teachers. There are actually two kinds of scientists. The dreamers and the skeptics. You need both a Fermi and a Teller to push forward science.

  • @cesaredecal2230
    @cesaredecal2230 4 ปีที่แล้ว +132

    This professor is awesome.

  • @mmattel
    @mmattel ปีที่แล้ว +36

    I am 57, just stumbled over this series of lectures. I feel like a fly just found the honeypot. Students can feel honored to have such a professional teacher. Thanks MIT for sharing.

  • @rhettsmedia
    @rhettsmedia 3 ปีที่แล้ว +49

    I’ve been in science for 45 years and this is the most exciting course introduction that I’ve ever heard go Mike short

  • @benkleschinsky
    @benkleschinsky 3 ปีที่แล้ว +142

    "I'd say your scientific knowledge is roughly around 1850." Pretty nuts to think about it that way.

    • @benartee9493
      @benartee9493 2 ปีที่แล้ว +3

      Maybe nuts but also spot on, no? I’m now understanding things I never got at school because questions were just left open. Probably similar to how Michael Short felt when he went to MIT as a high school student.

    • @hpholland
      @hpholland 2 ปีที่แล้ว +13

      Fun fact the term “Nuts” comes from a US General during the Battle of the Bulge (late 1944). So your colloquialism to describe your incredulity is a century newer than your scientific knowledge on nuclear physics :)))

    • @AJPMUSIC_OFFICIAL
      @AJPMUSIC_OFFICIAL 2 ปีที่แล้ว +5

      Impressive to see they went from not knowing about neutrons or electrons to the atomic bomb in less than 100 years.

    • @SplendidKunoichi
      @SplendidKunoichi ปีที่แล้ว +2

      @@benartee9493 see the thing is, I don't think it's been that way for a good while, a couple decades at least.
      in primary school they have you carrying around a periodic table for no reason in particular, but what it does is ensure your first ideas about the structure of things are motivated by particle physics and atomic theory, not anything out of newtonian physics or classical field theory; high school science is then almost all modern nuclear physics and basic quantum chemistry
      the principles of QM may be counterintuitive, but the fact that the theory is linear makes any of the math you do so much easier that this becomes actually irrelevant in the average curriculum. the historical narrative has more or less been turned on its head, attempting to find HS students' competence in any of the higher mathematics required by the earlier, more complete theories really seems like something they just don't have time for

    • @bunnyman6321
      @bunnyman6321 ปีที่แล้ว +1

      ​@@hpholland Interesting

  • @gladwolfy6097
    @gladwolfy6097 2 ปีที่แล้ว +20

    "we're all equal in the eyes on electricity" lol i love this guy

  • @ESTEEMUSA
    @ESTEEMUSA 4 ปีที่แล้ว +23

    Love the internet for this type of things that are actually free for us expect viewing some ads before to start and let creator earn and have money. Love it

  • @baoboumusic
    @baoboumusic 2 ปีที่แล้ว +17

    Some professors have the ability to make any simple subject extremely complex and unclear; this man does exactly the opposite. He takes an incredibly complex subject and explains it in such simple terms that it all seems to make sense.

  • @wrightmf
    @wrightmf 2 ปีที่แล้ว +11

    Old guy here, I wish I could have had a lecture like this back in the days simply to understand the process of producing a scientific paper (the nuclear stuff was straight forward).

  • @tyeauga
    @tyeauga 4 ปีที่แล้ว +44

    Thank You MIT. This is great stuff with a really good professor.

  • @dontmindmeimjustchilling
    @dontmindmeimjustchilling 10 หลายเดือนก่อน +3

    Im a physics undergrad student at a state school, and have been "taking" this course along with my regular coursework. Michael Short's teaching style is incredible!

  • @JASMINEJADE
    @JASMINEJADE ปีที่แล้ว +7

    as a new mechanical engineer going into the nuclear industry in the UK, this is incredibly useful and i'm shocked and kind of embarrassed the lack of nuclear basics I know / have been exposed to!! This is extremely helpful and I'm excited to follow this course.

  • @benartee9493
    @benartee9493 2 ปีที่แล้ว +14

    I’m so glad that the algorithm has presented me with a video by Michael Short. I am now embarking on watching this series of videos to switch off from my job as a banker. Also I have been highly skeptical of nuclear power which then makes it morally difficult to embark on financing the building of new nuclear power stations. I’m looking forward to gaining a much better founded opinion on this, whichever way my opinion will swing after this series.

    • @heysemberthkingdom-brunel5041
      @heysemberthkingdom-brunel5041 2 ปีที่แล้ว +1

      You will find that "both sides" are wrong, but one tends to be much wronger than the other, because some of those things cannot be simplified without then becoming wrong...

  • @runcycleskixc
    @runcycleskixc 2 ปีที่แล้ว +12

    I remember my first radioactive practical course in the former USSR. At the first safety briefing, the instructor (an old prof) said that there is nothing to be afraid of and that the amount of activity we will be handling cannot possibly hurt us. That was the end of the safety briefing after which we went on to pipet P32-labeled material.

  • @danielhuete8798
    @danielhuete8798 2 ปีที่แล้ว +5

    Sheeeeit, this guy is a good teacher
    you can totally tell why he works at MIT

  • @chriswaldrup9855
    @chriswaldrup9855 2 ปีที่แล้ว +5

    The greatest words I can give a professor . I understand

  • @patrickjordan3769
    @patrickjordan3769 2 ปีที่แล้ว +3

    I was going to make a comment about how good this instructor is...but then I realized everyone already said it so I liked their comments

  • @cherveny
    @cherveny ปีที่แล้ว +3

    I love that this class is available. My life took another path, but have always had an interest in the nuclear world. Looking forward to learning more from this course. Also work for an academic institution, and been a small part of them slowly sponsoring more open educational materials. Really hoping this trend continues and florishes.

  • @mmm-mmm
    @mmm-mmm 2 ปีที่แล้ว +1

    as an editor of scientific journal articles/technical documents, it's refreshing to hear a teacher talk about communication.

  • @moisessena1307
    @moisessena1307 4 ปีที่แล้ว +21

    Thanks for this course, MIT

  • @jodylowe8476
    @jodylowe8476 2 ปีที่แล้ว +5

    I watched Chernobyl recently and here I am.

  • @doosrabowler
    @doosrabowler ปีที่แล้ว +1

    This stuff is making me want to go right back to the start and give Physics a real go rather than bitching out at age 16 like what happened. Great teacher!

  • @pastorjerrykliner3162
    @pastorjerrykliner3162 2 ปีที่แล้ว +2

    Thank you for making these classes available online!

  • @JesbaamSanchez
    @JesbaamSanchez ปีที่แล้ว +1

    I believe Nuclear Energy is highly undervalued and under-appreciated, especially in today's energy and climate crisis. I do want to understand and get involved in Nuclear Energy this course I believe would be beneficial to understand nuclear energy and maybe look into applying with my Mechanical Engineering background. Thank you, MIT!

  • @ianprado1488
    @ianprado1488 4 ปีที่แล้ว +75

    "When can you throw out energy and momentum conservation?"
    When you are a cosmologist

  • @zunar_j5_933
    @zunar_j5_933 7 หลายเดือนก่อน +1

    I would have loved to have had this professor in college. Lucky folks!

  • @BB-wh3nm
    @BB-wh3nm 4 ปีที่แล้ว +8

    Thanks, this is my dream online course! ❤

  • @DSE_23
    @DSE_23 2 ปีที่แล้ว +7

    I should really get back to doing my own engineering homework, But this class is just so engaging I am procrastinating by watching other chemistry chemistry videos videos lol

  • @MTdirtrider
    @MTdirtrider 2 ปีที่แล้ว +2

    These videos are awesome!! Thank you for making them public. This professor makes me want to go back to school! 😁👍🏼

  • @ThunderKat
    @ThunderKat 2 ปีที่แล้ว

    This is like the best end road into the endless TH-cam searching...
    Educational videos, formal and informal both alike.

  • @xitheris1758
    @xitheris1758 6 หลายเดือนก่อน +1

    Greenpeace is an excellent example of the Dunning-Kruger Effect in just about everything, including environmental protection, but especially nuclear risks.

  • @egbertgroot2737
    @egbertgroot2737 2 ปีที่แล้ว +1

    This teacher is awesome .... each and every video he keeps me completely focused!

  • @georgeydlfc
    @georgeydlfc 2 ปีที่แล้ว +2

    What an enjoyable, funny and well presented lecture. This professor has really mastered his craft at delivering interesting information whist keeping it light and engaging. Thanks very much from England

  • @yaoifan420blazeit4
    @yaoifan420blazeit4 2 ปีที่แล้ว +9

    i ended up going to art school, but i had a deep interest in physics when i was in highschool. this is an awesome find for me - learning without the pressure of exams at the end of the semester!!

  • @swastikdiwakarsingh3006
    @swastikdiwakarsingh3006 3 ปีที่แล้ว

    Woahhh I've never expected that I'm gonna watch this on internet it's seriously awesome I'm so inspired from history lecture........... Thank you so much for such an awesome introduction ND to the channel who provide this.....

  • @antongerin4932
    @antongerin4932 3 ปีที่แล้ว +6

    Science lays in the history... Those crazy, deaf forests... I love it

  • @TheDeathSinger
    @TheDeathSinger ปีที่แล้ว

    thank you for making this open for the public, im a collage student trying to follow along as i love nuclear physics and this course is absolutely amazing

  • @iwayansuandi
    @iwayansuandi 2 หลายเดือนก่อน

    To be honest, I barely understand the math behind the explanation, but I know it's good stuff to listen to. When I feel i've learnt enough in life, I come to MIT'S open course to remind me that there students and professors are studying n explaining complex stuff and they take it so seriously; it makes me feel that I've wasted my time while other are busy learning. Thank you MIT for the FREE open course❤

  • @peterh5165
    @peterh5165 2 ปีที่แล้ว

    Good video! Thanks for making this video available to the general public. I especially liked your coverage of science and why it is important!

  • @Slowmotion1225
    @Slowmotion1225 2 ปีที่แล้ว +4

    Watching Kirk Sorensen talk up LFTR's made me realize how cool it would be to revolutionize energy production.
    I'm a 36yo truck driver with a high school education, so this is way beyond my ability to comprehend.
    If you're young, and taking this course, count yourself lucky. You could literally change the world some day.

  • @rhettsmedia
    @rhettsmedia 3 ปีที่แล้ว

    This is the most exciting class introduction I’ve ever heard I have two masters degrees in a BS degree material science and nuclear materials I would be very excited to take this course even with what I already know

  • @jacobjohn378
    @jacobjohn378 2 ปีที่แล้ว +2

    Seems like an amazing class, I am jealous of this education

  • @davidsmith5775
    @davidsmith5775 2 ปีที่แล้ว +1

    An extraordinary teacher that reminds me of the wonder (and fear) of being able to achieve the goals of higher education. The last 200 seconds is a beyond-brilliant caveat re: where we are mired...

  • @antonbashkin6706
    @antonbashkin6706 ปีที่แล้ว

    This is so cool, I'm really grateful I can sit-in on this class from home.

  • @lien-chinwei4815
    @lien-chinwei4815 หลายเดือนก่อน

    Thank you. Professor Short's lecture is very informative and well presented to me as a mechanical and software engineer, .

  • @thattubesound2214
    @thattubesound2214 5 หลายเดือนก่อน

    This is amazing! I wish he had taught some of my electrical engineering courses at University of Illinois. This whole series is terrific.

  • @ahmedsalem5725
    @ahmedsalem5725 3 ปีที่แล้ว +1

    Thanks for sharing knowledge in a good way.

  • @jackfanning7952
    @jackfanning7952 2 ปีที่แล้ว

    I appreciate having access to this material. Now do one on the future of energy production - renewables.

    • @mwg911hk
      @mwg911hk 2 ปีที่แล้ว

      Google it

  • @MAULIK9654
    @MAULIK9654 2 ปีที่แล้ว +1

    Awesome teacher and an elite communicator 👌🏽❤️

  • @icy_bird5540
    @icy_bird5540 2 ปีที่แล้ว +1

    This guy is a great teacher I can already tell I’m not the smartest person and I know that this guy makes me feel like this is something I can do

  • @alexyakyma1479
    @alexyakyma1479 2 ปีที่แล้ว

    Absolutely love your lectures.

  • @DarkStar-vx7rn
    @DarkStar-vx7rn 3 ปีที่แล้ว

    This is awesome for small town people with lots of wrk, thank you!

  • @phoenixlord2017
    @phoenixlord2017 2 ปีที่แล้ว +5

    Watching these videos makes me really intrigued by nuclear engineering. I am currently studying at the University of Minnesota Twin cities for Chemical Engineering, and I am not planning on switching degrees either, but I would definitely be interested in maybe completing a B.S. in nuclear engineering.

    • @moisessena1307
      @moisessena1307 2 ปีที่แล้ว

      Yes me too!! I've always wanted to be a nuclear engineer but right now I'm finishing the course in chemical engineering. When I'm done Im gonna do a Msc in nuclear engineering.

  • @justincross83
    @justincross83 2 ปีที่แล้ว

    Thank you Dr. Short!

  • @justgivemethetruth
    @justgivemethetruth ปีที่แล้ว +1

    This is really awesome ... and I don't normally use that word. Another good resource on understanding nuclear power - which we really need considering that nuclear is probably the only real clean energy generation method that can scale up to power the whole world.

  • @waynesmith3002
    @waynesmith3002 2 ปีที่แล้ว +3

    The math portion of your courses are way over my understanding........but curiously, I totally enjoy your presentations and look forward to viewing many more. I especially enjoyed your Chernobyl lecture.......thanks, Wayne

  • @bearlogg7974
    @bearlogg7974 5 หลายเดือนก่อน +1

    It takes you 2X longer to learn about the "comprehensive history of Chris Chan" than taking a MIT course in nuclear science

    • @Socialistdemon
      @Socialistdemon 3 หลายเดือนก่อน +1

      Intro to Chris Chan: section 1-18

  • @drcarlasouza6407
    @drcarlasouza6407 3 ปีที่แล้ว +1

    I work in KAERI... thanks for using our material

  • @bunnyman6321
    @bunnyman6321 ปีที่แล้ว

    This Professor is excellent!
    Thanks for sharing!

  • @Howtragicforyou
    @Howtragicforyou 3 ปีที่แล้ว +2

    Arguing with Greenpeace may not give you cancer but it definitely gives you an aneurism

  • @Ghostnotes1221
    @Ghostnotes1221 ปีที่แล้ว +1

    Very good and clear presentation.

  • @gabrielgutierrez2781
    @gabrielgutierrez2781 2 ปีที่แล้ว

    This was recommended by youtube and man what a great find!!!

  • @BusinessAnalyzer
    @BusinessAnalyzer 2 ปีที่แล้ว +3

    Prof. Short has done an amazing job explaining these concepts.
    I have been a "hobbiest" nuclear engineer (did not pursue it in full during university). I can easily understand the material. What I really enjoyed was the grading expectations for the course. Extremely fair! Even some great incentives to go that bit further and gain the priviledge to apprentice with the professor on some interesting experiments.
    I'm happily going to listen to these while I clean my room (A Dr. J. Peterson reference)

  • @Wordoflord11
    @Wordoflord11 5 หลายเดือนก่อน

    Thank you mit USA

  • @connorkelleher2537
    @connorkelleher2537 4 ปีที่แล้ว +18

    really wish I could just take a test after watching this and get some credits from MIT

  • @Bultish
    @Bultish 2 ปีที่แล้ว

    this is GOLD, cheers from Sweden

  • @brian5606
    @brian5606 2 ปีที่แล้ว +1

    Great video put in layman's terms of understanding 👍

  • @kidgrit
    @kidgrit ปีที่แล้ว

    the timeline where buster from arrested development was a really nice science professor.

  • @trekaddict
    @trekaddict 2 ปีที่แล้ว +1

    I'm nowhere near as educated as any of the people in the room. The only time I ever used E=MC² was during a physics test in high-school equivalent where I had forgotten the formula for energy. (Got full marks though!) and yet, I learned a lot from this.

  • @FF-kb4km
    @FF-kb4km 2 ปีที่แล้ว +1

    This Professor is awesome

  • @squidchurch82
    @squidchurch82 2 ปีที่แล้ว +6

    I wished this video series was available when I was in the 8th grade in the 1970's, I would of ended up being a nuclear engineer. Thank you for making it available!

  • @skitteryboospeedpaint6782
    @skitteryboospeedpaint6782 ปีที่แล้ว

    Casually hyper fixating on Chernobyl, Nuclear Power Plants, and Radiation poisoning.
    Genuinely these are the best videos in this fixation ❤❤

  • @mamun7891
    @mamun7891 ปีที่แล้ว

    WoW! The open minded MIT! Great Resources with a Great Teacher!

  • @nikunjrathod1671
    @nikunjrathod1671 4 ปีที่แล้ว +1

    This is great stuff

  • @mathbee
    @mathbee 2 ปีที่แล้ว

    I love his teaching style

  • @endingalaporte
    @endingalaporte ปีที่แล้ว

    the greenpeace part and environmentalist part : great

  • @renatopicollo
    @renatopicollo ปีที่แล้ว

    Amazing teacher. Thanks for sharing 👍

  • @laurengarner7911
    @laurengarner7911 2 ปีที่แล้ว

    So I'm literally a speech therapist, and I just wanted to know more about radiation after watching the Chernobyl series, and now I think I'm hooked on this lecture? I'm not supposed to like this...why is it so interesting???

  • @ianprado1488
    @ianprado1488 4 ปีที่แล้ว +2

    Yes! fantastic :)

  • @robertmccully2792
    @robertmccully2792 2 ปีที่แล้ว +2

    You can tell when a teacher knows what they're talking about when they can explain in such a way that anyone can understand. If you can't explain things simple, you don't know what your talking about.

  • @winnerd6772
    @winnerd6772 2 ปีที่แล้ว +1

    An awesome teacher ❤

  • @evanfinch4987
    @evanfinch4987 ปีที่แล้ว

    Thank you!

  • @srimuharyati2387
    @srimuharyati2387 ปีที่แล้ว

    Terimakasih banyak. Banyak sekali belajar dari video ini

  • @averagegamer-mx1of
    @averagegamer-mx1of ปีที่แล้ว

    I just wanna say thanks for making it so easy to learn nuclear physics and I hope to one day when I graduated hs to go to your school

  • @markrix
    @markrix ปีที่แล้ว

    The more people we educate about radiation, the less misinformation and hysteria we have about nuclear power. keep information free!

  • @fairysox221
    @fairysox221 4 ปีที่แล้ว +2

    9:21 Answer "The moment of the big bang theory" where the maths completely breaks down !

  • @user-tv9gk8df1u
    @user-tv9gk8df1u ปีที่แล้ว

    Great stuff!!!

  • @rubenbuitrago8305
    @rubenbuitrago8305 ปีที่แล้ว

    The teacher is awesome, I'm practically an illiterate compared to the students, and I understood a lot thanks to his explanations and the background I built myself through reading science divulgation books like "the goddamn particle" by Leon Lederman.

  • @vladpetric7493
    @vladpetric7493 2 ปีที่แล้ว +4

    "We're all equal in the eyes of electricity."

  • @_Olivers.Travels
    @_Olivers.Travels 4 ปีที่แล้ว +8

    I've been calling it the 60 Hz shuffle for about 25 years now....It originally debuted as the 400 Hz shuffle when I brushed against a power supply while working on a periscope.

    • @RammuDK
      @RammuDK 3 ปีที่แล้ว

      You rarely make that mistake twice. As a marine engineer, I learned a lesson about induction the hard way. I was installing the wiring to an additional CO2-alarm in the aft-most cargo hold, and had run the cable to the alarm in the cable tray in the engineer's passage way. Next to the cable were the 6,600 V power cables to the aft reefer trafos. So when I was almost finished and about to connect the cable to the alarm to the terminals in the junction box, I touched the wires and got zapped, and learned to factor in induction in the future :-)

  • @zack_120
    @zack_120 11 หลายเดือนก่อน

    15:35- the M and T equations here mingle mass with kinetic E without known their relationships - hopefully solved eventually somewhere forward.

  • @theguestofhannah9101
    @theguestofhannah9101 ปีที่แล้ว

    Electric charge is also conserved. Thanks for a descriptive presentation.

  • @Cherokeelion
    @Cherokeelion 2 ปีที่แล้ว

    Mike Short is a rock star!

  • @GeorgeSakala-gx6kl
    @GeorgeSakala-gx6kl 11 หลายเดือนก่อน

    😮😮😮u really are a great teacher it has really helped me with my physics task hoping to pass my exams with the knowledge I have gained

  • @magnusaugustus
    @magnusaugustus 3 หลายเดือนก่อน

    excelent lesson