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
You're a true legend sir... you never taught us to learn physics... you teach us to love it... really grateful to be able to learn and love it from you sir... love and respect from India
Thank you very much for your lectures. I have a mechanical engineering degree and working on my master, but I took all 3 physics courses from you. I wish I knew about these resources when I was taking physics. I hope you continue helping students around the world. Again, thank you! You're an excellent teacher.
Sir I am a 9th grade student From India. I want to become doctor and I used to love physics becoz your video make me love physics more and more...😍😍 Love you sir... You are a legend for those who wanted to learn conceptual things....😊
Dunno if thats jee or neet oriented or not but this is some op premium level content for sure! Seriously made me fall in love with phy, true to their words! thank you!
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!!!
Thank you for the amazing lectures. To me they are like a t.v. series I like. After watching one lecture, I get excited to see what the next lecture holds. I used to hate physics but now I am starting to see the beauty of it.
For the first time i really got into thinking in physics out of curiosity rather than just memorizing it .. Thank you very much sir .... Your lectures really helps me a lot
I love how these lectures by this brilliant man from years ago are helping me more than my professor's inadequate teaching style and his mickey mouse powerpoint presentations
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.
Walter Lewin, I want to show my deseo admiration for your great teaching career in MIT. You are one of most clever physics teacher i have ever heard in life. Im a 30 years experienced Civil engineer and I yet learn a new when i listen your lectures.
I am so MAD at myself that I found these videos and lectures by Prof. Lewin in March!!! Had I found them last year I would have watched all the lectures from starting to end they are JUST AWWWWWWWWESOME.... now hardly any time is left for NEET exam!!!
Professor Lewin, you are true so true saying that these lectures will make us love Physics. You are the best teacher in the world! Can't stop watching all of them.
Your the best teacher I've ever watched. Please allow me to pay you strong respect. I graduate of mechanical engineer about 20 years ago and I've been relearning many of the topics of those years through your lectures.
Thank you sir, Yesterday I demonstrated the modified engine to my students that you showed as an application of third law . The students were very happy to see such a beautiful demonstration. Your lectures made me love Physics and now I'm using them to make my students love Physics.
I am a student in the faculty of engineering, aeronautics and spacecraft from Egypt. I love watching the videos of your honor, Doctor, and your explanation is very beautiful.
sir, its great to learn from u. I never expected that i would be learning from a man who started giving lectures way before i was born. Love from India
Sir i am NEET aspirants and sir your lecture help me a lot i am sure next year i will clear neet exam with full marks in physics thank you so much sir 😊🙏
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.
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 :((((((
You can find ways of loving Physics without Lewin and loving History without whoever you think is the RU-vid "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.
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?
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.
Hi professor,i am student of class 9th from India and i have attended all your lectures thoroughly and you are really the best teacher i have seen so far.
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........
@@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.
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..
Thank you sir for your wonderful interesting lectures (which is very rare today cause the teaching quality has gone so down). This help us a lot. Love from India.
Which thread will break depends on the way you apply the force on the lower string.. Case1: the force was applied very fast Case2: the force was applied with a regular speed In case 1,the thread breaks due to the inertia of the mass because the random downward force couldn't create any tension in upper thread and to oppose any change inertia acted upward and the thread was broken.. But in case 2, the force downward force was added with the Mg which became greater than the Tension in upper string
sir i am a jee aspirant and i found your video lectures on 19th of september 2019 at 00:00am and from that time i have been constantly awake and i am not able to sleep because your lectures are just soo beautiful that i just keep watching them and cannot go to sleep. Thanks and huge respect for your efforts for such high quality education love from india
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.
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.
The assigned number of the lecture Hall 26,100 is really strange..! Sometimes I wonder what is the total number of such large lecture Halls at MIT ??? Here in India, I've never seen such an well equipped lecture hall.
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
Ive unfortunately had a crisis in my family. It'll initially probably sound funny but its not. My dad is a college educated 4.0 perfect attendence student with an AP cert in aircraft mechanics and has recently came to believe the bible says the earth is flat so in his mind it must be. This is very disturbing to all the kids which obviously know the earth is round. Now he has even my mom believing this bs becsuse she is very religious as well. And they love saying things like, if the earth is spinning at 1,000 mph why arnt we flying off into space. Well thank you professor i can now answer that mathematically with total confidence. Ive enjoyed the lecture so much ive went on to watch about 5 more so im learning alot! Thanks alot for sharing these lectures professor Lewin you are helping this guy out...
@@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*
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.
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 : )
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!
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.
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
Wow! Enjoyable and lively. Being a student teacher in Physics makes me feel the lecture indeed . This is absolutely amazing for sure. It confirms how real is Physics. I have to ape this and shape my profession too. Thumbs up.
I sat down to watch a few minutes of this. Was waiting for the twist at the end only to see that 49 minutes had already passed? You may not be a magician but you are a type of sorcerer for sure - mad respect to this teaching
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...
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*
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
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.
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*
when you pull it slowly, then the top string has grav of block and(+) the force of pull, yet the bottom one only got the pull; yet when you pull it fast, then the top one hasn't yet deformed, so grav only on the top one, (if the pull is large enough) then the bottom one will break.
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 ❤😃
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.
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 !!
I wish I could have studied under you. You are a grand master of science; I will be like you some day, with my own personality mixed in. You are an inspiration. Thank you for having lived.
Hey sir, I began to hear your class a few days ago. And from your lectures, as you say i began to love physics and yoir class is very useful to me, where i was having several doubts. But now all that was cleared. And to be frank I'm an introvert infront of teachers so i refuse to ask doubts and moreover it's fully online. But ur lectures help me to overcome my doubts 😊
Sir, I believe that the first string should have broken the reason being ...... When we pull the bottom string the tension force increases in the string and by doing so mass hanging is increased and so the tension must .........
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 !
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.
@@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?
@@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.
Thank you so much Professor Lewin ❤ for these amazing lectures! I can't express the quantity of doubts that have got cleared just by watching your lectures. You're surely the best physics teacher I've ever listened to and studied from.
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.
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.
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?
Sir may you live long . I am preparing for jee and the way you explain things so wonderfully is truly eye-opening to me . Although I missed the chance to be in your class but seeing you through my screen i think that was enough to make me love physics for the first time. You are a legend sir❤.
@@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...
Dear Walter, In this video last demonstration was nice, I got some point, how acceleration did major role here. For my better explanation, let’s consider Tensile strength of rope 20N/m^2 and Tension of top rope 15N by mass of Box, bottom rope tension Zero. On the first time pulled the rope faster, according to F=M*A, the acceleration increased suddenly in fraction of second, so the Force F increased suddenly that force applied on bottom rope it may higher than Tensile Strength of rope by this reasons bottom one rope break it on First time. On second time rope pulled Slowly, the acceleration increased gradually so force increased gradually from Zero assume when its reached greater than 6N, top rope will break because of tension on top rope now is 21N (15N by box + 6N by applied force on bottom rope) mean greater than tensile strength. Thank You .
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😇
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 ..
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..
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 .
if lower string is pulled with jerk then it will experience tension while due to inertia at rest of mass M , this force will not transmitted to upper string , so lower will break ✌️✌️✌️✌️✌️✌️✌️✌️✌️✌️
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
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
The last one answered is due to inertia when you pulled it very strongly the force on the bottom string broke it whereas upper string remain like that. But you took your time then it got time to transmit the force upwards due to which it broke
Professor, at 19:34, you say that the object 2 is pushing on object 1 with a force F21. But from Newton's second law, a force is responsible for accelerating a mass. Why wouldn't object 1 move to the left, and accelerate in that direction, when object 2 applies a force on it? Why does object 1 accelerate with object 1 to the right?
@@lecturesbywalterlewin.they9259 Yes, but why doesn't it move in the other direction, professor? Since a force causes acceleration, shouldn't it accelerate to the left?
@@adforfun3675 The force f21 doesn't act on the body itself. It's is exhibited by the body as a reactionary force. For example : when you shoot a gun... the gun applies a force on the bullet to push it forward (F12) and the bullet applies force on the gun and pushes it backward (recoil). So F21 acts on the body which is applying the initial force rather than the body on which the force is applied
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.
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 !
Thank you so much Prof.Lewin...I have always loved physics...but we are mostly fed formulas and questions instead of true physics. You are a game changer... thank you for bringing physics(real physics) to the table...you are a legend...❤
The difference is in the manner in which the force is applied. The lower string breaks when your applied force is abrupt and quick. However, the upper string breaks when the applied force is slow and sustained. The 2 kg. mass works against the lower string in the first instance, and against the upper string in the second. All is DEPENDENT on the manner in which the force is applied.
