Problem 213 - Nuclear Energy

[@KirkhamMotorsports1]

Professor Lewin, I have followed you for nearly 20 years now. I watched your videos with my sons as they grew up (we still watch them together). Thank you for this video. I deeply appreciate your love of physics and especially your love of sharing physics with the world.

[@lecturesbywalterlewin.they9259]

Wonderful

[@swatide5515]

​@@lecturesbywalterlewin.they9259idiot

[@me41shreythakur61]

A)Binding energy increases rapidly at the start as the atoms are small and forces of attraction are strong as the size increases the forces become weaker thus binding energy decreases. B)All the elements want to achieve stability so smaller atoms perform fusion and increase no nucleons and bigger atoms perform fission to reduce no of nucleons. Thus, trying to reach closer to fe56

[@lecturesbywalterlewin.they9259]

watch my solutions

[@L.NEVER.LOSES.]

TYPICAL JEE ASPIRANT RESPONSE

[@creativeworld_nm]

Wow Professor!! That's a new field for me. Thanks

[@Saddamhussien-uz5nb]

I had seen the sir 9 year ago when I see the sir today after 9 year I have tears in my eyes oh sir how much you become old

[@koenth2359]

Here's what I (believe to) know about it: (a) If we consider a stable nucleus consisting of nucleons on the one hand, versus those same nucleons separated by large enough intermediate distance on the other hand, then the nucleus contains less energy than the sum of the energy of the separate nucleons. The difference is called the binding energy of that nucleus and if we divide this binding energy by the number of nucleons, we get the (average) binding energy per nucleon. Although protons repel each other because of the Coulomb force, this is overcome - at very short range - by the strong force, which explains the fact that they are bound at all and have a lower total energy when bound. The mass of the atoms or ions can often be measured and when the mass of the electron cloud is subtracted, the mass of the nucleus remains. This will generally be lower than the combined mass of the constituent nucleons when separate. If the difference is Δm, the binding energy would then be Δmc², and the binding energy per nucleon then is Δmc²/A, where A is the mass number of the particular isotope. Radioactive decay will always release energy and therefore result in nuclei that have higher binding energy per nucleon. As a rule of thumb, the following factors generally favor the stability of nuclei: - neutrons and protons are around a certain ratio, which gradually increases from around 1 : 1 (for lower atomic numbers like He upto O) upto ratios around 1.6 : 1 for the heavier ones. For example, the most stable uranium isotope, U-238 has 146 neutrons and 92 protons. - an even mass number A (=number of nucleons). - an even charge number Z (=number of protons). - an even number of neutrons (A-Z) These factors combined may explain that ⁴He is such a favorable configuration that it is split off readily from less stable large nuclei, featuring alpha decay. When there are too many neutrons in a nucleus, we typically see that a neutron changes into a proton, emitting an electron and an antineutrino. This is called β- decay. When there are too many protons, we typically see that a proton changes into a neutron, either by capturing an electron from an inner shell, or by emitting an anti-electron and a neutrino. (β+ decay) (b) The arrow labeled ' Fusion' denotes that for light nuclei, fusion will result in heavier nuclei, with a higher binding energy per nucleon, whereas 'Fission' denotes that for heavy nuclei, fission (= splitting of the atomic nucleus) will result in a 'more favorable state', corresponding to a higher binding energy per nucleon. So fusion is an exothermal nuclear reaction in the region below ⁵⁶Fe and and fission is an exothermal reaction in the region above ⁵⁶Fe. This iron isotope itself (and a few around it, denoted by the blue bar) have the most favorable energy state, therefore they are very stable and it will not fission nor fuse, unless forced to do so by huge amounts of energy, like in the death of heavy stars.

[@lecturesbywalterlewin.they9259]

nice!

[@kumaraakarsh3756]

@@lecturesbywalterlewin.they9259 I would've mentioned it all , but you said to keep the answer brief, Sir.

[@evanaipoalani7198]

absolute gigachad, he's still going!

[@ArturoHernandez-y3k]

a) The graph represents the energy required to remove or add nucleons (protons or neutrons). This says that the ennery for removing a nucleon from iron(56) is higher than removing a nucleon from Uranium(235) b)Fusion: Occurs with lighter nuclei (A < 56), where the binding energy per nucleon increases as A increases. Energy is released when light nuclei combine. Fission: Occurs with heavier nuclei (A > 56), where the binding energy per nucleon decreases as A increases. Energy is released when heavy nuclei split into smaller fragments.

[@johnchessant3012]

Very interesting! And that is a very cool camera effect on your shirt

[@ulfhaller6818]

a) The plot shows how tightly nucleons are bound in a nucleus, depending on the size of the nucleus. Nuclei with a high binding energy per nucleon are more stable. The most stable nuclei are around iron-56, and both nuclear fusion (for light elements) and nuclear fission (for heavy elements) release energy due to differences in binding energy per nucleon. b) Fusion: In the lighter part of the graph (low A), smaller nuclei can combine (fuse) to form larger nuclei, releasing energy. This is because the products of fusion have a higher binding energy per nucleon than the original nuclei, which releases the excess energy (as in stars). Fission: In the heavier part of the graph (high A), large nuclei can split (fission) into smaller nuclei, also releasing energy. The fission products have a higher average binding energy per nucleon, meaning they are more stable, and energy is released in the process (as in nuclear reactors and bombs).

[@symbolspangaea]

You are a blessing to humanity. Thank you!

[@vagaxd]

just please don't get older you are a good man just don't go from this world

[@FerzanTapramaz]

a) As the mass number increases average binding energy per nucleon generally increases and peaks at about Iron, then slowly decreases. Since binding energy is negative energy, the iron nucleus is the most stable among other nuclei; fusing or breaking the iron nucleus costs energy. b) Since the iron nucleus has the least potential energy, other elements tend to transmute into Iron, though at different timescales. For lighter nuclei this transmutation occurs through fusion, joining of nucleons together, typically in stellar cores. For heavier nuclei, the change is through fission, breaking the nucleus into components, either spontaneously as in radioactive decay, or inducedly as in an atomic bomb.

[@sundaresswarn.g.r6288]

Great sense of passion towards teaching sir...

[@feelingzhakkaas]

Respected Sir...God bless you Always

[@WhoCares_Official]

The best Professor, you helped me so much and continue to help me with my Physics all through your KZbin MIT Lectures ❤

[@lecturesbywalterlewin.they9259]

Glad to hear that!

[@rafaelpadilla757]

Great idea to explore new territories beyond 8.01, .02 and .03

[@kamalkhandelwal3665]

This atomic mass number is crucial in nuclear physics as it represents the total mass of the nucleus (in atomic mass units, or amu). While the mass number is the sum of nucleons, the actual mass of an atom is slightly less due to binding energy (mass defect) that holds the nucleus together.

[@carultch]

A: the chart tells us the trend as a function of the total number of nucleons in each nucleus, for the amount of energy per nucleon in the nucleus. In other words, it tells us how much energy it takes to remove the average proton or neutron from the nucleus, if we were to take it apart completely, and turn it into free protons and free neutrons. We see evidence of this, when extremely light elements, and extremely heavy elements, have an atomic mass that is more than 1 amu per nucleon, and elements in the 20's for their atomic number tend to have an atomic mass of less than 1 amu per nucleon, with Iron having the lowest atomic mass per nucleon. Carbon-12 has exactly 1 amu per nucleon, but that is only because of our convention to use it for defining the amu. This also explains why free protons and free neutrons BOTH have a mass greater than 1 amu, since we have to invest energy in splitting atoms to make free nucleons. B: The element with the most binding energy is iron. Iron is the "valley" in the nuclear energy function, where it takes the most energy per nucleon to take apart the nucleus. Nuclear fusion turns smaller elements into larger elements, until they reach iron, and there is no more energy to extract. Nuclear fission breaks apart large elements like uranium, into smaller elements, until they reach iron, and there is no more energy to extract thru fission. It takes an addition of energy for fusion to create elements larger than iron, as happens during a supernova.

[@misterdubity3073]

I think the arrows indicate which way changes to nuclei occur in Nature. Larger nuclei split into smaller ones, smaller ones fuse into larger ones, always seeking a more stable state. Approaching an atomic weight of about 60 or 56.

[@WilliamEllison]

You're describing a concept related to nuclear stability in atomic physics. The atomic weight around 56, which corresponds to iron-56, is indeed significant in nuclear processes. The principle you're referring to is that nuclei tend to move toward a more stable state. - *Fission* is the process where heavier nuclei, typically those heavier than iron, split into smaller nuclei. This process releases energy because the binding energy per nucleon increases, making the resulting nuclei more stable. - *Fusion* is where lighter nuclei, like hydrogen isotopes, fuse together to form heavier nuclei, releasing energy in the process. This is because, for nuclei lighter than iron, the fusion results in a higher binding energy per nucleon. The element iron-56 represents a point of maximal nuclear binding energy, meaning it’s one of the most stable nuclei. As such, both fission and fusion processes tend to produce products that are closer to iron in terms of mass, as nature seeks this stable energy state.

[@hanslepoeter5167]

I found this plot, together with over 400 pages of other study. Didn't know about OER. That's good material.

[@balbodhjha4386]

Hello sir i am from India and have been watching you from past 5 years and you have taught me a lot in physics,so thank you very much I have a question which i am unable to solve and it isnt available on google i request you to explain this question in any of your videos Question:2 body if mass 11kg and 11.5kg are connected by a long light string passes over a smooth pulley.If end of 4s the string be cut,find the position of each body in next 2sec.

[@lecturesbywalterlewin.they9259]

watch my 8.01 lectures - your answers are all there

[@balbodhjha4386]

​@@lecturesbywalterlewin.they9259thank you sir

[@bindhyachalgupta5571]

So great Sir So great ability!! You are so great Sir

[@xtxnobody_coll]

i am from india and currently preparing for jee i watch your old lectures which always clears my doubt ..i wish i would have been your student in mit ❤❤

[@kmadhusudan9895]

Sir, this plot tells about the stability of nuclei. Initially the slope of the graph is very steep upto Fe-56 which has highest B E per A meaning for small increase in A there is a large increase in B E per A. Beyond Fe-56 the slope is gradually changing to flat implies less change in B E per A for large change in A. Left of Fe-56 lighter nuclei tendency to fuse to form heavier nuclei. Right of Fe-56 heavier nuclei unstable tendency to form stable nuclei by fission.

[@WilliamEllison]

Yes, your description is correct! This plot indeed represents the stability of nuclei, typically shown as *binding energy per nucleon (B.E./A) versus mass number (A)*. Here’s a breakdown of what you said: 1. *Steep Slope up to Iron-56:* Initially, the slope of the graph is very steep up to *iron-56 (Fe-56)*, which has the highest binding energy per nucleon. This means that as the mass number increases from light elements like hydrogen and helium, the binding energy per nucleon increases significantly. A steeper slope indicates that smaller increases in mass number (A) result in a large increase in binding energy per nucleon, signifying that the nuclei are becoming more stable. 2. *Flattening Slope Beyond Iron-56:* After iron-56, the slope becomes less steep, indicating a gradual flattening of the curve. This implies that the binding energy per nucleon changes very little for further increases in mass number. The nuclei beyond this point are not gaining stability as significantly, which makes them less stable compared to iron-56. 3. *Fusion to the Left of Iron-56:* Nuclei lighter than iron-56 have a tendency to *fuse* together to form heavier and more stable nuclei, as fusion increases their binding energy per nucleon, pushing them closer to the peak of stability. 4. *Fission to the Right of Iron-56:* Nuclei heavier than iron-56 are *less stable* and have a tendency to undergo *fission* to form smaller, more stable nuclei, which have a higher binding energy per nucleon, moving them closer to stability. The key takeaway is that *iron-56* represents a peak in nuclear stability, where the *binding energy per nucleon is maximized*. Both fusion (for light nuclei) and fission (for heavy nuclei) are processes that lead nuclei toward this peak of stability.

[@purushottam8048]

Sir, from my opinion, this curve plot depicts about the stability of atomic nucleus.At first, binding energy per nucleon starts to increase rapidly upto atomic no 20(may be) and increase slowly beyond atomic no 20 and becomes maximum for iron-56 and then starts decreasing accordingly. This curve shows that both heavier and lighter nuclei are unstable due to less B.E per nucleon .Above atomic no 80 ,the elements are heavier and unstable.In order to increase BE per nucleon for gaining stability,they undergo nuclear fission. Below atomic no 80, the elements are lighter and unstable.In order to increase BE per nucleon for gaining stability,they undergo nuclear fusion. Thus ,for the stability of atomic nucleus,it must have greater BE per nucleon.

[@WilliamEllison]

Ever wondered what makes certain atomic nuclei stable while others aren't? 🤔 Let's dive into the fascinating world of nuclear physics and explore the *Binding Energy per Nucleon Curve!* *Key Points:* 1. This curve represents the *stability of atomic nuclei* by plotting *binding energy per nucleon* (B.E./A) against the *mass number (A).* 2. *Binding energy per nucleon* rises steeply for light nuclei and reaches a peak at *iron-56 (Fe-56),* which is the most stable nucleus. Beyond iron-56, B.E./A gradually declines. 3. Nuclei *lighter than iron-56* can become more stable by *fusing* together-this process increases their binding energy per nucleon, driving them closer to stability. 4. *Heavier nuclei* (those beyond iron-56) have lower stability and tend to *undergo fission* to split into lighter, more stable nuclei, thus increasing their binding energy per nucleon. 5. *Iron-56* is the star of the show! 🌟 It has the *highest binding energy per nucleon,* making it the most stable. The universe naturally trends toward nuclei with higher B.E./A because *higher binding energy means greater stability.* 6. To sum it up: Lighter nuclei undergo *fusion,* heavier nuclei undergo *fission,* and the goal is always to get closer to *maximum stability.* *Why It Matters:* Understanding this curve helps explain why *stars shine* (fusion of light nuclei) and why *nuclear reactors work* (fission of heavy nuclei). Nature always seeks stability, and this curve is the key to understanding how that happens! If you enjoyed this little dive into nuclear physics, give this video a like, and subscribe for more awesome science content! 🔔✨ *#NuclearPhysics** **#BindingEnergy** **#Fusion** **#Fission** **#Iron56** **#PhysicsExplained** **#ScienceIsCool*

[@Jiya-b9u]

Best professor

[@darkomalic5950]

a) This plot represents the relative stability of nuclei according to their composition. The nucleus which has the highest BE/nucleon is the most stable nucleus that can exist, and it turns out that ⁵⁶Fe occupies that role. All nuclei show differing values for BE/nucleon, but none as high as ⁵⁶Fe. b) Because ⁵⁶Fe is the most stable nuclear configuration that can exist, every nucleus tends to form it if able. Stars are comprised of hydrogen and helium, and therefore use fusion to turn them into more stable nuclei (according to the plot) UNTIL they reach the state of fusing nuclei to form ⁵⁶Fe. Once this state is reached, no further energy-efficient fusion is possible, thus, the star collapses in on it's iron core, resulting in a spectacular explosion. Heavy elements also have a tendency to form ⁵⁶Fe, but in order to do that they must lose nucleons from their cores. We call this radioactivity. They can, for example, undergo fission, a process of splitting the nucleus apart, in order to reach a more stable state.

[@lecturesbywalterlewin.they9259]

you better watch my solutions

[@johnnolen8338]

Hello Professor Lewin, It's been a minute or two since I answered one of your problems. I'd like to try to answer this one. Just a guess as I haven't studied nuclear physics seriously in over 25 years, but I believe the arrows indicate that Fusion implies an increased mass number while Fission is exactly opposite, mass number decreases if Fission occurs. Cheers, my friend. 🤓

[@lynnxuanluo]

Hello, Professor. Take care. Hope you are doing well.

[@ISRAELCHERINET]

I LOVE PHYSICS BECAUSE OF YOU SIR 😢😢😢😢😢❤❤❤❤❤❤❤❤❤❤❤❤

[@ultimatedoug2227]

a general question, what happen to the energy of a photon when it undergoes redshift while coming from faraway galaxies. where does the energy go

[@lecturesbywalterlewin.they9259]

when a photon is emitted which is red in the frame of the star which emits then we will see a shorter wavelength if that star is moving to us with a high speed (a longer wavelength when the star is moving away from us) (google relativistic Doppler Shift). Shorter wavelength mean higher energy. The Doppler shift does change the energy of light, as it alters the frequency of the light wave, which is directly related to its energy; a higher frequency corresponds to higher energy light (like blue shifted light), while a lower frequency corresponds to lower energy light (like red shifted light).

[@kathyfrejoles775]

Sir, I am from the Philippines. I am an avid follower of your lectures!

[@lecturesbywalterlewin.they9259]

I am honored to have a follower from the Philippines.

[@kathyfrejoles775]

@lecturesbywalterlewin.they9259 Sir please continue posting lecture videos. I am happy to see your video last night. I hope you are keeping yourself well!

[@shripadkusnurkar]

respect for your age what a energy you have sir

[@lecturesbywalterlewin.they9259]

So nice of you

[@ipq88s]

Hello sir, after your advice i have been loving to solve physics problem more and more. Thank you so much sir, you are turly a hero❤

[@85481]

I'm a chemist so i'm probably over simplifying but my understanding is that fusion of elements up to Fe produces energy and fission of all elements above iron also produces energy. So above and below Fe different nuclear processes are energetically favoured. I haven't done this sort of thing in some time so apologies if this is poorly described.

[@lecturesbywalterlewin.they9259]

watch my solutions

[@SohamVerma-l9s]

I am studying from physics wallah. Our physics teacher Saleem sir taught about this graph in modern physics

[@ottofrank3445]

Groeten uit Amsterdam! Komt u toevallig binnenkort weer naar Nederland? Ik zou u heel graag nog een keer op NL'se tv willen zien. Fijne dag !

[@lecturesbywalterlewin.they9259]

ik was 3 maal op De Wereld Draait Door kzbin.info/www/bejne/b4C2hp2ep7Oaj7c kzbin.info/www/bejne/nJTPlmicZZV4fq8 kzbin.info/www/bejne/rHnPm41tdqZgnbM kzbin.info/www/bejne/m2rMnIBraN-Vb9U

[@pete7971]

It looks like a decay curve of an element. The graph is not focused well so I can't speak further. It's been said when the universe evolved, elements were limited up to iron, then further elements especially iron evolved. With the fusion further complicated elements arrived. So the graph shows iron as the basis of further elements. Different number of neutrons developed different elements but also these various elements shown are from decay.

[@Glancing_Dagger..]

sir how's your health I'm worried about you please take some rest😢❤ love from india

[@The_Green_Man_OAP]

If you're worried, maybe you could offer him something to increase his longevity..? Whatever he gets, I'll have. :)

[@kumaraakarsh3756]

Ans A) meaning of this plot: This plot represents the dependence of "the energy required to disintegrate a nucleus" or the "energy required to hold a nucleus together" on the mass number (A) . Ans B) Nuclides on the left of Fe fuse together(Fusion) to achieve a suitable N/Z ratio and get stable. Nuclides on the right disintegrate (Fission) to get a suitable N/Z ratio and get stable. The process also includes a series of decays. P.S. I have been away from Nuclear Physics for quite some time. Hope that I still make sense. Nevertheless, still being a friend of you is an honour Sir 🙏 Further addition to comment: 1. The N/Z ratio for stable nuclides is about 1 for light nuclides but almost 1.6 for the heaviest nuclides because of the increasing influence of the electrical repulsion of the protons. 2. The N/Z value for stable nuclides is about 1.3 at A=100 and 1.4 at A=150.

[@WilliamEllison]

Your explanation makes perfect sense, and it's great that you're revisiting these concepts! You nailed it with the descriptions of the plot and the behavior of nuclides. *Answer A* accurately describes the "binding energy per nucleon" plot. This plot shows how the energy required to either disassemble a nucleus or keep it together changes with mass number (A). It highlights that the most stable nuclei (like iron-56) are at the peak, with the highest binding energy per nucleon. *Answer B* explains the stability process well. Nuclides lighter than iron (left side of the plot) tend to undergo fusion to increase stability by getting closer to an ideal neutron-to-proton (N/Z) ratio. Nuclides heavier than iron (right side) tend to undergo fission and other decay processes, aiming to become more stable as they too approach a better N/Z ratio. These processes aim for stability by maximizing the binding energy per nucleon. And hey, it's always a pleasure discussing these topics with you. You still got it! Thanks for the kind words-being a friend to you is equally an honor. 😊🙏

[@kumaraakarsh3756]

@@WilliamEllison Thank you for your valuable comment. May I know if you Are authorised to reply on behalf of Sir Lewin ? Thanks & Regards

[@surendrakverma555]

Thanks Sir for posting a good problem. Regards

[@nuclearphysicsbyrs8766]

I m your stdnts sir 🙏🙏🇮🇳🇮🇳

[@AnshikaVerma-i2b]

Hello professor you are great in the world thankyou 🎉 teke care hope you doing well...... I first time i am watching your video you are amazing person in the world 💞💞.... I pre to th god Live love 😘😘

[@lecturesbywalterlewin.they9259]

keep watching!

[@The_Green_Man_OAP]

William Ellison's comments are good enough for a mention, imho. I'm no nuclear physicist, so I refer you to him.

[@gaussdog]

HelloHelloHello….is now how my wife and I greet each other …. 😁🥰

[@mohamedgamal-l4c]

looking good as always

[@giornoGiovanna964]

What is it on the background oscillating their

[@Vengeance167]

The pendulum is always there🙆🏻

[@danishnaseer9808]

Hi sir from where can a get the pendulum its really cool toy

[@aayoushsinghthakuri7]

I loved ur videoss❤❤❤❤❤

[@rashishsaini50]

sir is rocking that outfit

[@The_Green_Man_OAP]

RIP to the fallen🕯️🕎

[@beatricecristea]

Dear Professor Lewin, My name is Beatrice Cristea and I am a first-year student at École Polytechnique de Paris and I am very, very passionate about physics. Throughout my educational journey, I followed your physics courses at MIT and they helped me a lot to advance, to understand physics and to perform in this discipline. The way you explain makes it seem like everything is very simple and it helped me develop a special love for physics. Now, at the University, I have a project to take an interview of about an hour with a professional who inspires me and who works in my field of interest, in order to be able to decide in the choices regarding my future career. Although I am aware that your time is precious and you have a busy schedule, I would be extremely honored if you could grant me this interview! Thank you very much and have a nice day!

[@lecturesbywalterlewin.they9259]

very kind of you but I no longer do interviews \\/\//////

[@georgejetson4378]

@@lecturesbywalterlewin.they9259Not even for $1 billion ?

[@babulalsoudagar1178]

How are u sir Walter Levin

[@redhiredgaming5722]

Hello Respected Lewin Sir I am from India High School, I want to ask we beleive so much in quantum mechanics and everything including devices around us are a proof of correctness of QM but sir cant it be the way we see and observe atomic scales and if we go into the atomic world in real life things arent like QM tells at all? Pls answer I am a big physics enthusiast

[@lecturesbywalterlewin.they9259]

QM is very very different from classical Physics. It's also very non-intuitive. Goolge the word *"entanglement"* That's impossible in classical mechanics. But it's the way the world ticks.

[@redhiredgaming5722]

@@lecturesbywalterlewin.they9259 Thanks Sir! So much; But cant it be possible that QM might not exist when we see from perspective of an atom or it does? Maybe QM is the way we see/observe micro scales from sub-macroscales and they all work as theyre not wrong but relatively wrong!

[@lecturesbywalterlewin.they9259]

@@redhiredgaming5722 what you wrote is nonsense

[@redhiredgaming5722]

@@lecturesbywalterlewin.they9259 Ok sir I really apologize to disappoint you!

[@johnvuch]

I think I'll get my pole and net and just go fission.

[@samkelomotsa8106]

Wonderfull Professor

[@lecturesbywalterlewin.they9259]

Many thanks

[@ankit1985-sk]

Sir Lewin ,I am jee aspirants i am in class 12 th currently and how to manage my 11th revision

[@MAGnetICus_Attractus]

❤ with my dyslexia I get the 2 F words mixed up. So I would probably get a F on your question 😂. FissION is like a fuel rod in a reactor core and FusION uses compressION/FrictION? Or do i have them flip flopped? 😂

[@Kmrvoltage]

Legend❤❤❤

[@akhand_rao]

Sir what is the machine behind you, is this operated by electrical energy?

[@lecturesbywalterlewin.they9259]

perpetuum mobile

[@mandmlandscapeshortlife]

I like your videos it has really helped me in rigging limbs although I don't understand a lot of the formulas your real life applications of physics has really opened my eyes thanks.

[@mandmlandscapeshortlife]

Especially about 🌈

[@FrodoBaggins.1]

Hello, mister Lewin! A question not related to the problem presented in this video - there is a youtube channel named "potentialg" which is uploading a large number of short videos of your lectures. Is that channel yours, too? KZbin recommends me more of that channel's videos, than your channel's. Wishing you a wonderful week!

[@lecturesbywalterlewin.they9259]

*thanks for mentioning this. I did not know it. It's a gross violation of my copy rights.*

[@FrodoBaggins.1]

@lecturesbywalterlewin.they9259 I greatly appreciate your love for physics and for knowledge, and your desire to share it with us and to show us the path towards understanding it. It is sad to see such incompetent people stealing your work to make money for themselves. Search for that channel and report it. Wishing you and your wife all the best! ❤️

[@lecturesbywalterlewin.they9259]

@@FrodoBaggins.1 I will make every effort to get "potentialg" off the air. *It is a GROSS violation of my copy rights.* *All of you can (and should) watch my videos in my channel*

[@kamalagrawal]

hello professor lewin i am a huge fan can you guide for person from india to get into MIT

[@lecturesbywalterlewin.they9259]

read MIT's admission site

[@Shortclip1303-j3x]

Sir I need help because I learnt and understand a concept but can't solve questions. Please tell how to improve these problems

[@kumaraakarsh3756]

Maintain a notebook and solve atleast 25 solved examples on a particular concept,from different sources. You will learn how to utilise concepts in different scenario. Then start attempting unsolved problems. Refer to solved examples if and when required. Do not hesitate in asking doubts. Practice this continuously for a month, and reply here. Good luck!

[@PawanYadav-nj7vg]

Why the object behind you never stops its to and fro motion, although there is friction due to air?

[@lecturesbywalterlewin.they9259]

it's magic

[@The_Green_Man_OAP]

​​​​@@lecturesbywalterlewin.they9259 Kinda like Stan Meyer's water car? How did that work? I'm thinking it's got something to do with radio (or _micro_ ?) waves as a power source or inducer for electrolysis.

[@carultch]

Google Autofill answers the question. Start searching "perpetual motion machine", and you'll see "batteries for perpetual motion machine" is one of the recommended related searches. There's usually a hidden battery that makes so-called perpetual motion machines work.

[@Shashank-1-1]

Hi sir i am your biggest fan Sir can you please tell me how to crack *NEET*

[@lecturesbywalterlewin.they9259]

Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam* You will find all information you need on this channel in three playlists "Homework, Exam, Solutions & Lecture Notes". 8.01 & 8.02 will each take about 200 hours, 8.03 about 250 hours.

[@Abhishek-ti5er]

❤.

[@chbullaiah6247]

Did u remember me sir???

[@Klug2424]

Is he using a different camera?

[@mohamedyoussefFahim]

in 5 of October the moon will be close to Venus

[@lecturesbywalterlewin.they9259]

Venus is now very bright!

[@Deadlyvipergamer]

Sir do you believe in God's just asking

[@lecturesbywalterlewin.they9259]

No I don't but I respect all who do

[@aayoushsinghthakuri7]

Hello sir 1st viewer

[@feconicuzngageasse8306]

Hi sir

[@ultimatedoug2227]

i do get your point, but this concept that the wavelength of light increases in redshift is so embedded in me, you said energy is conserved in a frame, but if you had a way to measure the energy of a photon at each instant without interacting with it in some frame, would you see the energy of the photon stay constant or decrease with time. if it is constant then why is there a redshift happening, and if it isnt then why is energy lost

[@lecturesbywalterlewin.they9259]

*energy may NOT conserved if you change your reference frame* In the ref frame of you drving your car, you have no KE. But relative to a bystander you do have KE.

[@ahmedomarabdallah2052]

😅

[@godisgood2482]

Hey

[@zander-j4k]

hi

[@SalmanFarsi-bs6jt]

❤❤❤ first view ❤❤❤

[@Ambar_Tomar_official]

❤love from india ✨may you get age✨ I didn't find ans on whole internet Sir u r my last hope plz🙏🥺 How can Pascal law be wrong here ? ➡️One end of U tube is opened and other is closed if we write Pressure @ height h from upper end for both arm then P for open end arm = Atmospheric pressure + density × g × h P for closed end arm = density × g × h 🙄A/c to Pascal law Pressure should be equal @ same height for a liquid but here Pressure on open arm is greater due to atm pressure. Plz respected sir solve my doubt 🙏

[@kumaraakarsh3756]

Any increment in pressure gets transmitted throughout the liquid undiminished

[@lecturesbywalterlewin.they9259]

correct

[@kumaraakarsh3756]

@@lecturesbywalterlewin.they9259 Sir, Is my above comment correct?

[@The_Green_Man_OAP]

Here's a comprehensive answer: Glass U-Tube with Liquid and Atmospheric Pressure A glass U-tube is a device used to measure pressure differences between two points. One arm of the tube is open to the atmosphere, while the other arm is connected to a pressurized gas or liquid. The tube is filled with a liquid of known density (ρ). Atmospheric Pressure The atmospheric pressure (P0) is 101,325 Pa (1 atm) at sea level, which is the pressure exerted by the weight of air above the surface. This pressure is constant and uniform throughout the atmosphere. Pressure in the U-Tube When the liquid in the U-tube is at rest, the pressure at the open end (left arm) is equal to the atmospheric pressure (P0). The pressure at the sealed end (right arm) is the sum of the atmospheric pressure and the pressure exerted by the weight of the liquid column (ρgh), where g is the acceleration due to gravity (9.8 m/s²). Equation Using the hydrostatic pressure equation, the pressure at a depth h from the surface of the liquid is: P = P0 + ρgh Example Suppose the length of the horizontal arm (l) is 21 cm, and the ends of both vertical arms are open to atmospheric pressure (P0 = 101,325 Pa). A liquid of density ρ = 1,030 kg/m³ is poured into the tube, filling the horizontal part. The height of the liquid column (h) is the same in both arms. Using the equation above, the pressure at the sealed end (right arm) would be: P = 101,325 Pa + (1,030 kg/m³ × 9.8 m/s² × h) For a given height h, the pressure at the sealed end would be higher than the atmospheric pressure due to the weight of the liquid column. Pascal Pressures The pascal (Pa) is the unit of pressure in the International System of Units (SI). It is defined as one newton per square meter (N/m²). The pressure values mentioned above are expressed in pascals. In summary, the glass U-tube with liquid and atmospheric pressure measures the pressure difference between the open and sealed ends, taking into account the weight of the liquid column and the atmospheric pressure. The equation above relates the pressure to the density of the liquid, the acceleration due to gravity, and the height of the liquid column.

[@Awatar20k]

First

[@Glancing_Dagger..]

I can see a Buddha statue behind you sir... Buddhism is a part of sanatan DHARMA❤

[@ultimatedoug2227]

@lecturesbywalterlewin.they9259 i meant to ask what happens to the lost energy of the photon. where does it go during the doppler red shift

[@lecturesbywalterlewin.they9259]

if a star sends only one photon in our direction then this one photon exerts a force on the star in the opposit direction as photons have momentum (they have no mass). That force is independent of the speed of the star relative to us. The speed of the photon on its way to us never changes. It's always c relative to Earth, also c relative to the moving star. In our reference frame the photon will always move with the speed c even if the star moves towards us with speed 0.5c. However, the wavelngth of the photon in the Earth frame is different from the wavelength in the frame of the star and that is due to the fact that the star moves to us with speed 0.5c. This is called relativistic Doppler shift. All light from the star that reaches us 0n Earth will be shifted towards the blue (blue shift). The energy doesn't come from anywhere because the light ray hasn't gained any energy. The difference between the energy of an object in two different reference frames is a meaningless quantity. Energy is conserved in a given reference frame. But there is no reason that the energy must be the same across different reference frames. In fact, it's not. Energy is a frame-dependent quantity. So you may see a light ray with some energy, but someone moving relative to you will see it with a different energy. This is not unique to light either. Driving in your car, you observe your car to have zero kinetic energy. But someone on the ground will observe your car to have some non-zero kinetic energy. Again, energy is conserved, but it is not invariant between frames.

[@PhysicsSorcerer]

Hey