8.01x - Lect 6 - Newton's Laws

Newton's Laws
Assignments Lecture 5, 6, 7 and 8: freepdfhosting.com/95e6843397.pdf
Solutions Lecture 5, 6, 7 and 8: freepdfhosting.com/4984cbb7f1.pdf

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*Of the century

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I was there ❤

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@@crazyboy-yi9iw dream on

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Wht is 26.100

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Sir you dont teach physics rather you teach how to think & feel physics....

[@lecturesbywalterlewin.they9259]

+Mahfuj Anam Thank you

[@vibhavarisaitwal]

it's true

[@sudeepreddy645]

Yes is true

[@elyelmo84]

@@lecturesbywalterlewin.they9259 Professor, which year could be this lessons recorded, I have wondered about it lots of times

[@aloksrivastava9169]

@@lecturesbywalterlewin.they9259 Every action has an equal and opposite reaction

[@sceKernelDestroy]

6th lecture: Newton's Laws ------------------------------------------- 00:20 Newton's First Law and Inertial Reference Frames 06:55 Newton's Second Law (F = ma) 14:14 Newton's Third Law (action = -reaction) 20:28 Various Examples of the 3rd Law, e.g. Heros engine (aeolipile) 26:25 Consequences of Newton's Laws, e.g. strings under tension

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Thanks

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2 years later, your legacy of helpfulness lives on.

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[@lecturesbywalterlewin.they9259]

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used to? btw I am also in 9th grade

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@@MentallyAbled i think he doesn't love it anymore

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[@connynordgren3679]

Great! This lecture was a reward for me. The first five was very informative and I have to study hard to understand everything. Now Newtons three laws was easy to understand. Thanks a lot!!!

[@lecturesbywalterlewin.they9259]

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I've been self-studying physics for 6.5 years, and now have curtailed my imagination to the basic laws of motion (Euler and Cauchy too) being that I'm truly a martial artist at heart. I always see at least one thing new it seems in each rendering of Newton's laws.

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:)

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[@lecturesbywalterlewin.they9259]

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[@lecturesbywalterlewin.they9259]

+Phuong Nguyen Thanks for your kind words.

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[@lecturesbywalterlewin.they9259]

26-100 means building 26, "room" 100. 1 means first floor, thus it is room 00 on the first floor. There are at MIT only 3 lecture halls about as big as 26-100

[@animals42life8]

@@lecturesbywalterlewin.they9259 top or bottom string, it depends on sudden or gradual pull.. correct professor lewin?:)

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[@lecturesbywalterlewin.they9259]

@@harleydavidson1014 I am glad you are now educated. As far as Flat Earth people is concerned: Flat Earth is a religion with many followers. Religion is about BELIEFS regardless of the FACTS. Science is about verifiable FACTS regardless of one's BELIEFS. *NEVER EVER argue with anyone about their religion. It's anyone's right to believe what they want to believe even if it is pure nonsense (like the Flat Earth Religion). Rotating Earth video apod.nasa.gov/apod/ap190825.html *Ask all Flat Earth crazy friends to explain the following.* A total lunar eclipse can be seen by many people on Earth. Depending on where you live on Earth you may see the total eclipse shortly after sunset (the Moon is then near the horizon) or *at the very same time* high in the sky at night for people much further East on Earth where the sun has already set many hours ago. For all those who see the total eclipse near the horizon the umbra (shadow of the Earth near the Moon) should be a horizontal bar if the earth were flat but *it is ALWAYS a perfect circular disk no matter what the elevation of the Moon above the horizon is*

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[@lecturesbywalterlewin.they9259]

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[@lecturesbywalterlewin.they9259]

Thank you

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Ahhh, you trickster, you. Changing your speed as you pulled! I would have voted for the top one too, but immediatly as I saw you pull it really fast I knew you made the bottom one snap on purpose! Making it snap before there is time for the block to even move.... Afterward, knowing the trick, I would have remained one who would not vote. Yet another brilliant lecture sir, emitting love for this amazing subject.

[@lecturesbywalterlewin.they9259]

:)

[@physicshacks6349]

@@lecturesbywalterlewin.they9259 Sir can you please explain me ,the last string block demonstration . Why the upper string didn't break ?

[@inchbyinch4985]

@@physicshacks6349 acceleration....

[@kanak7488]

I just started 9th grade studies in my summer vacation and the first chapter in my textbook is Laws of Motion, thank you sir for this lecture, helped a lot.

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[@andyde1809]

Thank you professor, another very nice lecture!! In the final experiment of the 2kg block is possible to see that the bottom string breaks only if the increase of the tension is very rapid. In this case, I think, the system has not the time to reach equilibrium and the bottom strings undergoes to higher tension in respect to the top string. If instead the tension increases slightly than the top string breaks because of the gravity in the 2kg block. Does anyone agree with me?

[@lecturesbywalterlewin.they9259]

when I pull very fast the block has no time to move down thus the lower string will break. Only when the block moves down will the tension in the upper string increase.

[@andyde1809]

Thank you!

[@divyanshupandey5481]

@@lecturesbywalterlewin.they9259 I read all the comments just only to get answer from you. Thank you, professor. Huge #LOVE & #RESPECT from #INDIA

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Omg i passed

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For jee aspirants, this wasn't a big deal. I am sure, 40-45 thousand students must have answered correctly

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He fleshes out Newton in his teaching . Great lecturer

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Hello sir.. Take my Love and respect form Heart..i am a new student.. I have to say something.. As we know your class lecture make students study easy and joyful. when we start our journey as a science students at age 14 we don’t get wonderful lecture like you. Some of our teacher teaching us only reading book..we just Write and read we read formula Newton law,gravity, etc but teacher not show us real example..and for understand we only read some example in our book..for this reasons many student afraid in science. Next they give up and read another deperment..at early age we need study with fun, some practical example, that's why we love physics more and more... I believe if we get good lecture we can do better..

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Sir love your teaching luv from India

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Thank you for the superb lectures. Your sincere love of education and comes through

[@dongguodan2128]

For the last question: when pull the string slowly, the force due to F can be delivered to the top string; but, when pull quickly, the bottom line breaks before the F is delivered to the top string.

[@aniljangra3107]

My intuition is like that , when first lower string is being accelerated , still upper string gets higher downward force, but lower string because of acceleration gets elongated fast upto breaking point (after getting plastically deformed) but in this fast span ( lower duration of time) the upper string didn't get enough time to get plastically deformed....that's why lower string gets break. In second case , ( where as well upper string bears higher load ) upper string gets enough time to elongate, as lower string is not being accelerated , therefore upper string got broken........

[@Trilochan21265]

Right

[@shahidanowar1614]

So all depends on how fast he pulls it?

[@Krishna-iy9vb]

@@shahidanowar1614 I think so. That was the difference of the two repetitions in the video

[@wazeerali9487]

Sir plz tell us how you do this

[@welkinator]

@@wazeerali9487 So by applying a steadily increasing force to the handle under the red cube the force is distributed gradually through the system. When he jerks on the handle the mass of the cube initially resists (inertia) the force in an outward (upward) direction which creates opposing forces within the string that then breaks at it's weakest point. So why does the upper string always break first with a steady pull? Likely because it is longer. Both strings will deform (stretch) but the upper one will lengthen proportionately more than the lower string. The diameter of each string will decrease as the lengthening increases but the upper one will always be smaller than the lower until the point of failure. BTW, this is just my guess.

[@keviniqbalrodriguez1706]

This is dude is literally one of the best lecturers I’ve ever seen!!!!! I’m watching this as a refresher on Newton’s laws, and I was able to learn a lot more than I thought I would! Wish I had a physics teacher like this :((((((

[@lecturesbywalterlewin.they9259]

:)

[@ranjeettate8676]

You can find ways of loving Physics without Lewin and loving History without whoever you think is the KZbin "God". Lewin didn't have Lewin. I didn't have Lewin, but I found Feynman (in grad school, when I was going to teach physics!) and Eric Mazur, and Howard Zinn and Jared Diamond for History. I did poorly in Physics in college, not because I didn't have Lewin, but because I wasn't ready.

[@tusharkantiroy5568]

I find no higher learning in this lecture but Certainly have too, as a 15 age boy it's also clear to me that can help and give a crystal clear concept from this to anybody perhaps a college student or lower age class pupils, because the basics are all same, I thanks you from India, lots of respect too

[@pravitsacademy3673]

About the red cube problem. It depends on how fast Prof is pulling the string. The key is that forces are not instantaneous, they take some time to propagate. We you were fast the bottom string broke because the force couldn't reach the upper string. Nice demonstration.

[@fkurcik]

40:45: When you calculate forces in wires from condition of equilibrium, then the upper wire is more loaded (as he wrote on blackboard). However, there is a difference in how fast he applies the force. Without analyzing this deeper, I believe it's the inertia of the cube that resist's the impulse of force, which is reducing the load in upper wire. So, you can get two different situations, based on how quickly you pull the wire. Is this correct?

[@candleintheclass9361]

.

[@sheetalagarwalla1241]

Yes absolutely correct

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Dear sir, are your lectures enough for Indian exam JEE (Mains and Advanced)?

[@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. Homework and exams are posted below the video thumbnails. *I guarantee you that you will then not fail the Physics portion of any exam*

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The homework and exams, wrap your head around them, fondle, love and re-reason around them, that's the trick.

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Brilliant!! I wish I had a professor like you..

[@backyard282]

When it comes to the cube and the strings: in principle the top one should break first as predicted by his equations, however when he pulls very fast the tension in the bottom string increases so rapidly that it breaks before the tension in the top string has the time to increase to the breaking point.

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?? Didn't get it bro

[@andrewsanders5092]

Watching one of these video's makes more sense to me than an entire semester of Physics 1 has in college.

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Thanks a lot sir...this lecture helped me to solve many confusions about gravity and 3'rd law..

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You will be teaching for centuries for upcoming generations ❤Respect:)

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The channel name is so real. He did make you fall for physics. I'm currently preparing for IIT-JEE examination and so just to brush up my past concepts i open this video. Oh Man, such a great teacher ❤😃

[@lecturesbywalterlewin.they9259]

All the best

[@mdmobasshir595]

@@lecturesbywalterlewin.they9259 Made my day sir 🥺❤ Your Reply

[@PaulSmith-rx8rh]

Thank you for sharing your lectures! They actually made me love physics. They were fundamental for my decision to do Electrical Engineering in college. You are awesome, professor. Thank you for everything.

[@lecturesbywalterlewin.they9259]

Paul you are most welcome!

[@deependrachoudhary10th-a81]

@@lecturesbywalterlewin.they9259 uh

[@sanjibsaha8347]

Sir you don't teach us physics , you involve us to love physics and we fall in love in physics from HEART THANKS A LOT 🙏

[@TheNC100]

In the last example left open the key point is that the strings are not inextensible. The upper string would always break if the string were almost exactly inextensible (well, the cube should also be perfectly rigid with no way to deform it). Please correct me if I'm wrong. BTW: your lectures are so wonderful. I love the fact that you put so much emphasis on showing with experiments each single theoric result. Theory beyond physics is wonderful, but physics is not mathematics: physic laws are correct until someone proves them wrong, so it is crucial to put to the test the theoric results. You are very insistent on this and I appreciate it so much.

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this professor of physics is a great master of this scienze and indeed a master of pedagogy because of the way and

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The best lecture ever.. Thank you professor..Will be useful for my JEE preparation.. :)

[@lecturesbywalterlewin.they9259]

:)

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Hope you clear jee with 360/360

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Did you cleared jee

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U cleared JEE??

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The fans need to know.. did you clear JEE?

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You're the best teacher ever! I'm from Brazil and i'm learning A LOT with you classes!! I can't understand so well because of my english, but it's easier to understand than in my school!

[@PedroRodrigues-ld9qf]

Thank you so much Lewin!

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Greatest regret of my life that din't have a passionate teacher like you in my entire student life. And discovered you in youtube after end of my student life 😔.

[@fabriziotabasso1694]

Now that I have discovered Walter Lewin's lectures I wake up every day excited to learn new concepts and I see physics from a different point of view. I was already a big fan of physics, now I also have good resources to improve and expand my knowledge. I'm not english mother tongue but Walter Lewis's lectures are easy to follow and understand because everything is logically connected and beautifully explained. I'm studying physics in an undergrad course in Australia and I don't like my professor at all, but maybe it is not his fault, it's just hard to compete with a professor like Walter Lewin. Thank you for all the time and efforts you have put in your lectures.

[@lecturesbywalterlewin.they9259]

+Fabrizio Tabasso thank you for your kind words

[@aryan9393]

sir, I just got my physics exam score with just a measly 50/96 on the exam. I just found your lectures and really like the way of teaching. Kindly wish me luck for the next test (light, reflection, and refraction). I am in to not fail the next one !!

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Ooof class 10

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I don't know why these guys are so serious during this interesting lecture...just feel the beauty of physics.....and fill yourself with full of dopamine😇

[@user-wo5dk3qn7c]

In last string experiment, the whole thing was based on first law. When string pulled instantly the upper string and mass were still in rest and till the force reaches there the string broke

[@vatsinshah9635]

I am not out of high school yet. I am using your lectures presently to prepare for my ap. thank you so much for the uploads. Your videos have helped me a lot : )

[@lecturesbywalterlewin.they9259]

:)

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How is your life now.

[@marccowan3585]

The string which breaks depends on the time over which the force is applied? That is that it as though the information that the bottom string is being pulled has not yet reached the top string yet? Perhaps I am wrong, but I believe I heard somewhere that it has something to do with the speed of sound in the material? Great lecture by the way, my new favourite thing on youthbe

[@lecturesbywalterlewin.they9259]

The only way that the tension can increase in the upper sting is for the block to go down. But if you jerk at the bottom string there is no time for the block to go down (inertia). Thus the bottom strong breaks. If you pull slowly the block can easily and slowly go down, thus the upper string breaks first is the tension in it will then always be larger than in the bottom string.

[@allroundersupport104]

I am a Bankura Zilla School student, West Bengal, India. Our science teacher Soumitra Pati sent us this. Lovely video❤️

[@haseebulhassan1019]

Love from Pakistan. You are a great mentor. I’ve graduated as a mechanical and watching your all videos. Very helpful

[@muhammadsaimiqbal1551]

why uni bro?

[@edman2740]

On the red cube problem, I'm not entirely sure but doesn't it depend on the acceleration of your hand professor? I mean if you go fast there is little time to change the inertia of the object, therefore if you go slow there is enough time and you end up breaking the top one ?? Love the lectures btw, thanks for uploading them !

[@michaelwang1730]

It depends on the force you pull. If you pull slowly, then the tension will increase in both strings uniformly, and the top one breaks. If you pull quickly, then the bottom one already reaches the maximum force before it ever reaches the top, and so the bottom string breaks.

[@siamsama2983]

@@michaelwang1730 but that's coz in reality the string is somewhat elastic. If the string was inextensible, then surely the top one would break always?

[@carultch]

@@siamsama2983 Inextensible strings don't really exist. They are a theoretical limiting case, to simplify the mathematics of a problem where the string's extension under load is negligible compared to the motion involved in the problem. In a theoretical inextensible string, the forces would travel through the string infinitely fast, and the upper string would always break. But such a string could not exist in reality, as elastic response in general is limited to the speed of sound in the material.

[@riscy00]

I enjoyed this with closed caption, thank you!.

[@user-um9sl1kj6u]

I used to play ball with my nieces, and I wish I had done more… every day in life is a teachable moment for kids, whether it’s science, physics, or critical thinking, ethics, or math….

[@abelhgds]

Really well constructed and effortlessly understandable. Thanks!

[@jeanlatour9151]

the idea that I can shake the world made my day :-) Also loved the final string experience. Such a nice way to test intuition and so stimulating for reflexion ! Thanks for this lecture !

[@lecturesbywalterlewin.they9259]

:)

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@@lecturesbywalterlewin.they9259 :,-):^) 8-) ;-) ;) }:‑)

[@physicsbyprofmateen6631]

Respected sir Walter ! you are my ideal teacher . I proud of you . i love your way of teaching .. You are great .. you my mentor. sir can i use your experimental portion of videos in my videos ?

[@raihanshaik]

Sir my love for physics is incomparable to you but I feel physics in my inner heart and your leactures are just vvvvvv amazing. I wondered if taught for IIT jee exam then I would be your first student. When I will grow up I will meet you once for sure

[@seanderobillard5765]

Apparently if you watch all 94 of his MIT lectures starting with 8.01 and complete the homework/exams in the description of each video, Walter guarantees you will pass the physics portion to ANY exam. So yes, everything he teaches us here can be applied to IIT jee exam

[@sushilbhardwaj_]

Sir u r god for me I hated Physics earlier but now I m in love with Physics bcoz of u 🤗🤗🤗🤗🤗 Love uh sir Long live walter sir 😊😊

[@Rohirat2026]

Thank you very much sir. I easily learn this topic. You are great sir.

[@parthpatel6517]

When professor pulls string at high speed, red box deosnt move due to its higher inertia, and so bottom one breakdowns. And opposite in other case.

[@henryrubio8534]

Great lecture, I wish my professor taught us all this with as much enthusiasm as you have.

[@lecturesbywalterlewin.they9259]

:)

[@joshuagoodman5274]

I believe the string that broke - either the top or bottom - was relative to the rate of acceleration. I noticed that when the average acceleration was high, the shorter one broke - too much force and not enough time for the force to travel through string. And, when the acceleration was gradual, the top string broke because the average acceleration was lower.

[@harleydavidson1014]

Thank you professor Lewin! I have to share a quick story hopefully youll enjoy. Recently ive unfortunately had a crisis in my family thats tearing it apart. Initially this might sound funny but its not for the families dealing with this. So my dad is a college graduate. 4.0 perfect attendence student that recieved his AP cert in aircraft mechanics so he is educated but recently these conspiracy theory flat earth vids have convinced him that the bible says the earth is flat so him being super religious and my mom as well they both think the earth is flat. They love saying things like "if the earth is spinning at 1,000 mph why arnt we flying off into space. Well professor, thanks to you i can confidently answer that question mathematically. I enjoyed the lecture so much ive went on to watch about 5 more. So thanks again hopefully by learning physics i can explain to them that the flat earth is impossible and bring my family back to reality and stop all the fighting between the parents and kids. If anyone reading this enjoyed it please like it so maybe the professor will see it at the top...

[@lecturesbywalterlewin.they9259]

Flat Earth is a religion with many followers. Religion is about BELIEFS regardless of the FACTS. Science is about verifiable FACTS regardless of one's BELIEFS. *NEVER EVER argue with anyone about their religion. It's anyone's right to believe what they want to believe even if it is pure nonsense (like the Flat Earth Religion). Rotating Earth video apod.nasa.gov/apod/ap190825.html *Ask all your Flat Earth crazy friends to explain the following.* A total lunar eclipse can be seen by many people on Earth. Depending on where you live on Earth you may see the total eclipse shortly after sunset (the Moon is then near the horizon) or *at the very same time* high in the sky at night for people much further East on Earth where the sun set mnay hours earlier. For all those who see the total eclipse near the horizon the umbra (shadow of the Earth near the Moon) should be a horizontal bar if the earth were flat but *it is ALWAYS a perfect circular disk no matter what the elevation of the Moon is aboe the horizon*

[@sharks3010]

It's always impressive to me how he draws his dotted lines.

[@kundangupta4266]

you just have to hold the chalk perpendicular to the board and boom..

[@tomoakhill8825]

At 10:30 he explains that mass is an intrinsic property of matter, and not dependent on a force. In fact 4 years after this lecture the General Conference on Weights and Measures which defines the International System of Units, redefined the kilogram in terms of three fundamental physical constants: The speed of light c, a specific atomic transition frequency ΔνCs, and the Planck constant h. Using these numbers, it is possible to build an instrument the reads the mass of an object directly from the object.

[@mishmessythoughts]

Sir you are a genius, I am very near to JEE and for the love of physics, i am watching all your lectures as they are not very long. I love it. Thank you very much for existing 🥰 We all love you from India ❤

[@user-zv1wl9so1d]

Thank God that your lectures are recorded شكراً دكتور ولتر لوين

[@lecturesbywalterlewin.they9259]

:)

[@wazeerali9487]

@@lecturesbywalterlewin.they9259 sir plz tell us about last experiment how it may be possible sir plz tell us

[@bobthegreat3627]

@@wazeerali9487 If he pulled the string fast, the bottom one would break, since it won't get the time to reach the upper one Ans if he pulled it slowly, the top one would break...

[@ritikkumar5562]

Sir you say that body move with constant velocity along straight line...why are you used word( along straight lin) ..if you said constant velocity...

[@lecturesbywalterlewin.they9259]

if the line is not straight then there must be ab acceleration to change the direction of the veloscity, thus there must be a force

[@ritikkumar5562]

Sir but it is not necessary to used straight line word with constant velocity...because constant velocity give information that magnitude of speed and direction remain constant...so sir it is not necessary to used straight line word with constant velocity ..

[@ritikkumar5562]

Sir constant speed along straight line is perfect....in compare of constant velocity along staraight line.....am I right or wrong sir.....you are my god sir...please reply me..

[@ritikkumar5562]

Sir please tell me....please please .....your every word of physics is very important for me...you are my god....sir you say constant velocity along straight line...are you wrong .

[@CaptainCalculus]

I'm going through these again professor for my students and to get the highlights. FYI there is currently a motion before the international weights and measures authority to name the unit of momentum (1kg.m/s) = 1 Galileo

[@rishabhbajpai8340]

I m preparing for jee advanced exam and these lectures are very helpful for me.