I am preparing for IITJEE and I started detesting physics , love for chemistry and maths increased but by watching your lectures sir , a new love for physics emerged in me . Thanks a lot.

Hallo Prof. Lewin, believe it or not, lately as i come back home from the office, i watch your video while having my dinner. It feels like i was watching a TV serie. I am a postdoc now but everytime i see your taped class i feel like i was a fresh student in a senior high school. i really love the way you teach..

35:15 reminds me of a trip to Hawaii. Went to the top of the volcano in Maui (about 10000 ft) and drank a plastic bottle of water. I put the cap back on and drove back to sea level. The bottle was completely collapsed by the atmospheric pressure. Most impressive demo to my wife.

As an Engineering Student, I have always loved your Lectures, Professor Lewin. They've helped me a lot throughout my courses.

I love how the camera randomly zooms in on students taking notes

About the last experiment at 48:10: Mr. Lewin is draining all the air which is in the hose at the beginning by sucking in an amount of air that is subsequently released through the nose while blocking the end of the tube with the tongue. Doing so he creates a "vacuum" and the atmospheric pressure does the rest, basically it pushes the juice all the way up until it reaches a state of equilibrium. Assuming the juice has the same density as water, Mr. Lewin could suck the juice up to ~ 10 meters, maybe 11 meters if the human body has the capacity to generate a pressure equivalent to 1/10th of 1 atm. If we do this with a high density liquid the result would be way different. Thank you Mr. Lewin for sharing your passion with all of us and all the love and effort you put into these lectures. Greetings from Canary Islands. :)

These lectures are truly a treasure, not only are the lectures themselves being offered at no charge but also a set of homework problems along with their solutions. Thanks a lot!!!!!

Hello, Prof. Lewin. I am from India and have been following your lectures in 11th and 12th. Currently, I am in medical school and even now your lectures help reinforce the concepts and clear any doubts that may arise as one studies a topic. Thank you so much for uploading your lectures and helping hundreds and thousands of students around the world. Great fan of your lectures and your works and researches in Physics.

they have a freaking rifle in class.... this is the most awesome lecture ever !

When he uncovered that rifle I could barely believe it. Great professor.

The Professor"s lectures are more comprehensible than the Adverts that accompany them.

This man is the reason im interested in physics, that silky smooth voice MMMMMMMMMMM i could listen to his lectures for hours

prof. Lewin.......I read your book..for the love of physics and that also brought me to here..you are indeed as good as they say...it was super fun attending this lectures..in india...my local school teachers never teach with such methadology which makes physics interesting as much as u are making

Thanks professor for existing in this world!

So that was actually the atmospheric pressure itself which was responsible for the high level of Cranberry juice. Suckling the air out of the pipe did that trick. You are a awesome teacher. Your lectures will inspire students for 100 of generations for sure.

professor this Sunday i have competitive exam and your lecture is very useful so thank you!

Helps greatly to understand concepts of basic physics. Thank you professor.

This man is crazy ❤️ Wish I could get a teacher someone like him. You're the reason of many students who has started to love Physics again, Professor Lewin.

I'm immensely grateful to have these courses available for free here, and become a better engineer, and hence, a better man. Thank you professor, I will contribute to return the favor. 🙏the only thing I would suggest to add, is an explaination of what pressure is at the molecular level. I found it very helpful to understand why fluids behave in these strange ways, and to connect the concept of pressure (collisions) to temperature (agitation).

Every lecture of Professional Walter Lewin piques my interest and love for Physics. Thank you Professor Lewin.

All that I will say is that I completely agree with the name of this channel. Watching these videos really makes you love physics. I have loved it since many years now. Nonetheless, it is a delight to watch these videos. Thank you for your passion for sharing your knowledge and making us understand how the universe works, Mister Lewin! It is great to have you! I wish you and your family a very happy and healthy new 2024 year!

You are a great treasure to the World! 🙏

Wow you are amazing professor!!! Before watching this I always wondered how pascals law is consistent with the law of conservation of energy...Thanks a lot...

There was only like button but i loved the leacture !!! 😊

For the last question : When you SUCK air you are effectively trying to create a vacuum inside your lungs, so the model which is being recreated here is a barometer with water in it . And equating the pressure developed due to the juice to the atmospheric pressure we will get a certain limiting height (10meters for water) the hose is shorter than that so you are able to drink the juice.

I was doing similar experiments at home some time ago and i was just as surprised as you about how many percents of a vacuum i could get. It's actually enough to create a strong enough vacuum for certain experiments. I found another way of measuring the vacuum or overpressure by the way and it takes a lot less room. Fill a hose with water and trap some air at the end of the hose then close that end. If you suck on it and the air bubble doubles in size then obviously you've managed to lower the pressure to half an atmosphere. So it's easily possible to draw a scale on the hose, that indicates the pressure. Great lecture by the way!

Hey ,as a 14 year old, and physics enthusiast I am truly addicted of your lectures.

sir your lectures are awesome, it is a real love of physics

I really enjoy your lectures. Such a great teacher

I was learning about it 7 lessons and didn’t understand anything. After 2 minutes of watching it taught me more than during my science class. Thank you!

you made me fall in love with physics, thank you teacher

I’m here because of my homework. And I really like the explanation! I enjoyed the video and you earned a new subscriber :D. The name of the channel is correct: this makes me love physics (but I also liked it before ;D)

I have a lot of cleaning up to do, but do realize people sometimes rewatch your lectures while cleaning! We just need to listen to it all again (which is better than TV)

you are breathing out all the air inside the hose with the help of your nose (letting air out) so that you can suck more air afterwards from the hose itself ,up till the cranberry juice comes to your mouth (removing all the air),and also their will be some height at which you can no longer suck the juice up because of the atmospheric pressure.

Way better than any movie, way better

this is the best lecture ever

Professor, regarding the question at the end of the lecture: the earlier demo had shown your lung to be capable of 0.1atm overpressure for both inhalation and exhalation. In the final demo, you use this inhalation several times to get the juice up to you. The height it rises over each inhalation depends on lung capacity. You exhale through your nose while keeping the end of the hose in your mouth. Probably, you have closed that end using your tongue. (Those creates a barometer like situation) One more observation: if it were water, for hose length > 10m, the water would slip down to the 10m level each time you are not inhaling. This means that the maximum length of the hose for water can be 11m for an overpressure of 0.1atm

Sir I am from India and your lecture is really awesome

i used to wonder why everyone watched and admired walter lewin , now i get it a mad science lover who also loves too teach and does dare to any experiment I will never forget this lec prolly and i wished i had studied under u

had a very heavy headache, but that doesn't stop me to watch till the end. Much love Prof!

sir i got to know about u by physics wallah and tommorow is my physics test and ur class helped me a lot , huge huge thanku and love from india ❤❤😊😊

The best lecture ever

You don't know how happy I am. Thank you

Idk why but I can still understand his lectures at 1.5 times the speed.. awesome lectures

very great explaination ive just feel the physics right now

Sir you always make us love physics

love u sir and your great lecture..

In the sucking experiment in the first case the pressure was generated with the lungs, in the second one with the mouth. Mouth can generate greater pressure or vacuum than lungs because it's smaller in volume and its muscles are comparably strong.

Very clearly explained... You are the best physics teacher... Initially I didn't have any interest in physics, but your lectures addicted me to physics... May I know what inspired you to become a physics teacher?

I tried the snorkeling thing when I was a kid, I went to the beach and I tired to improve my hold breath time, so I dove with a plastic bottle and the idea was: when I reach my time limit i grasp air from the plastic bottle. I couldn't pull a single gram of air; even when squeezing the bottle I had barely enough air to reach my lung. almost drowned myself, but I learned a valuable physics lesson that day.

I wish I had lectures like these, my current fluid mechanics teacher is using paint for online classes

you are amazing,professer..the last part made me giggle alot..thank you

About the last qs: Probably you were squeezing the end of the tube by your fingers repeatedly for maintaining pressure difference made by each inhale and also to have a time for the next inhale. Thus creating enough vacuum for atm pressure to raise juice (maximum at 10 meters). Correct me if it is not the case.

sir it helped me to clear my concepts for jee. Thank you so much.

Lovely lectures❤

It’s about time you all figured it out.

What wonderful man like you! All my life I hate physics due to teachers. It's unfortunate that I lost that opportunity in senior school to be watching videos like this. I love your teaching method professor. I learned better through visually seeing things how they happen in real life. Any video related to biophysics in the series? Thank you sure much:)

Sir I think in the first case as u said just do in a one blow,the air in the chest after one blow would run out but in the second case u may have lifted the liquid just by sucking it many times as u are free to do.

Sir you are awesome. I wish I have a professor like you in my school.

The atmospheric pressure on the surface area of the juice that you drink up is (I'm guessing) about 10x that of whats pushing on the fluid in the manometer simply because its in a wider vessel and has more surface. Its basically just the hydraulic jack in reverse.

These lectures are great treat for all physics lovers

regarding experiment with air suction case 1: U-shaped tube: you did a single breath and since your lungs/chest can't expand more the liquid moved by one meter and stopped case 2: straight tube: the pressure in a tube is reduced not using your lungs but with mouth muscles. Thus you were able to reduce pressure gradually and release the air trough your nose (while closing with a tongue.

best lecture professor i never seen teacher like you............................if this lecture would be convert in Hindi ideo then most of the students would get benefit of this .............

16:34, did he roll the chalk to make those dashed lines?! How to make dashed lines so quickly is worthy of a lecture itself... Until then, thank you so much for sharing these on youtube!

SIR...YOU ARE AMAZING!

I think that the answer to the last question is; as he sucks up the liquid he is actually expending his chess so the low pressure in the chess equilibrates with the 1 atm in the tube by raising the liquid, and he seals the tube with his tongue to breathe out and sucks again and so on. You can suck up to 10 meters (water), at 10 meters the hydrostatic pressure equilibrates with the atmospheric pressure so if you try to suck from that point you need to generate under pressure (in Mr. Walters case it is a 1 m extra, assuming the water won't start boiling). Please correct if I'm wrong. Greetings from Turkey.

Great and bizarre lecture! And I think the answer to the question of why the height is higher than one meter which is what was obtained in the previous experiment is the following (what I think and I'm not sure): Assuming the pressure generated by the professor's lungs is the same in both cases, the reason the height is higher is; because in the first case (manometer) the atmospheric pressure is against the pressure exerted by the professor's lungs, while in the second case it's assisting the professor in sucking in the juice since the pressure exerted by the professor is the same but in this case, is negative hence dP would be: 1 atm - (-P) = dP = 1 + P atm where P is the professor's "suction pressure".

I am preparing for Neet and it is very helpful for me thanks🙏🙏

Wow...... That was awesome 👌

Very good lecture Sir. 🙏🙏🙏🙏🙏 Thanks and Regards 🙏🙏🙏🙏🙏

Great lecture! I wonder whether in the first manometer experiment the limiting factor is not so much the pressure the lungs can generate, but rather the total amount of air they can expire (5-6 litres). With a rigid pipe, the same amount of air might generate a much higher pressure than 0.1 atmosphere? Easy to check by repeating the experiment with a pump, limiting the amount of added air to 5 litres (which would give the same result, not explained by pressure limitations of the pump) or by using a rigid pipe (which would give a large pressure if the volume explanation is correct) for comparison? For snorkeling, deeper depths would still be a problem, as breathing in and out of a large tube is expected to lead to low oxygen and increased carbon dioxide levels over time as exchange of gas with the air outside the tube would be too limited. Whether inhaling in at 2 meters below the surface of a pool is feasible is fairly easy to check with a rigid pipe?

Love you Sir, thanks

This was awesome man! Love your teaching always! But, experiments to the level of using guns in class? OH YESSS!!!😊👍👍👍

I got the answer anyway. thanks for the cool videos

At the end, I believe in the previous example, you can only go about 1 meter because you are pulling nearly the entire weight (mg) of the liquid by your sucking force. At the end, you have the weight (mg) of the liquid in the container, not yet in the tube, assisting you. It would probably not get difficult until the E(Fy) in the tube and in the container are slightly unbalanced in the negative. I.E. Mtube*g >= Mcontainer*g.

🙏 God Bless Harmony Sithole for introducing me to this man.

Had you proceeded in steps for the first try(snorkeling), that level difference could have gone higher than 1m as well(right ?). While driving all that air out in one go instead, you were pretty much also reaching the sustainable strain limits of the lungs.

Hello professor, hope that you are in a great state of health and jovial as always.In your book "For the love of Physics" , at the end of the chapter "The Magic of Drinking with a Straw" you pose a question that whether we can snorkel much farther down beneath the surface of a lake or sea using the same trick that you employed in sucking the cranberry juice up to 16 feet. Well, I think the answer is NO.Because in the classroom when you are sucking the juice, every time after sucking when you can't take any more air in you exhale and start sucking again.But you can do that easily because the pressure on your chest is only 1 atmosphere.When you are beneath a water body, in order to inhale you need to expand your chest to a sum total of atmospheric and hydrostatic pressure which will increase with depth and thus you cannot repeat inhalation many times.Please let me know if I am thinking along the correct path. Thank you.

🎯 Key Takeaways for quick navigation: 00:34 🌊 Pressure is defined as force divided by area, measured in pascals (N/m²). Pascal's principle states that pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid and to the container walls. 02:00 🌬️ In a static fluid, the force exerted by the fluid on any surface must be perpendicular to that surface, as any tangential component would set the fluid in motion. 04:04 🚗 Pascal's principle allows for the creation of hydraulic jacks, where a small force applied over a larger area can lift a much larger weight. 05:28 🛠️ Hydraulic jacks do not violate the conservation of energy; work done to compress the fluid on one side is recovered as gravitational potential energy when lifting the weight. 07:20 🌍 Gravity affects fluid pressure; as you go deeper into a fluid or down into the ocean, pressure increases due to the weight of the fluid above. 11:49 ☁️ Atmospheric pressure, also known as barometric pressure, is due to the weight of the air above and is generally considered one atmosphere, roughly equivalent to 1.03 x 10⁵ pascals. 16:30 💡 Torricelli's barometer experiment demonstrated that the height of a liquid column in a tube is directly proportional to the atmospheric pressure, with mercury creating a column of about 76 cm. 26:09 🍷 Historical experiments were done with various liquids, including red wine for barometric measurements, and showed that liquids with different densities require different column heights to maintain atmospheric pressure. 30:57 ⚖️ Cornelis Van Drebbel built one of the first submarines in the early 17th century, around 1622, which could operate at a depth of about five meters with half an atmosphere of hydrostatic pressure. 35:10 🌊 Atmospheric pressure exerts significant forces, as demonstrated by the collapsing paint can when the air inside was evacuated. 36:43 🏊 When snorkeling or scuba diving, it's essential to counteract the hydrostatic pressure with pressurized air, as the forces can be immense. Snorkeling depth is limited by the ability to generate an overpressure in the lungs. 46:03 🍹 Contrary to lung limitations, a long tube can be used to siphon liquids from considerable depths due to different principles, like atmospheric pressure and gravity. Made with HARPA AI

You know , you have a lot of fans in China! The ideas were explained so clearly and the experiments were so interesting!

Ah so this is where KZfaq has taking me at 1:30am

3:28 this observation is also applicable to Brazil's colloquial language

I really like his enthusiasm to teach, as if he created physics. Loved all his work and have been a great inspiration. No one will match Professor Walter Lewin, not even Einstein ( cause Einstein's accent is a bit German which confuses me a lot what he is lecturing about😅😅😂)

Another great course. One thing I don't quite understand on the snorkeling. When I was 12 my father and I went snorkeling and dove up to 10 meters deep to the ground of the sea where a boye was. With no pressurized air how can our body sustain that amount of pressure? I understand that the gas in the blood is neglectable (as long as you didnt intake pressureized air) and the only problem are the lungs, but I am still amazed. My only guess is, that the few liters of air are beeing compressed and the rips are flexible enough?

For the final demonstration it does not matter how many draws you take, approximately 1m head of water is all the chest cavity can deliver. What is actually happening is Professor Lewin is using the smaller volume of the mouth cavity and strength of his tongue to generate the reduced pressure and to seal the tube between draws while simultaneously isolating the lungs from the tube pressure. This is the normal method of sucking everyone instinctively knows as an infant. To draw up a liquid using lung pressure risks inhalation of the liquid into the lungs, a potentially dangerous method.

These are the best lectures ever. thank you so much. What happens if I dive under water 2m f.e. with a bucket of air and try to breathe in there. would that work or does the same rule apply for the snorkeling?

Physics is love Physics is life!!!!

Dear sir, do you have a chapterwise playlist or i have to search individually for each lecture?

Pascal's Principle is exactly applicable in 0 gravity ( in the iss )

I think I got it. In the last experiment he was not pulling all of the liquid at the same time like in the first one. The liquid that remained in the beaker continued to be pushed down by atmospheric pressure, while the liquid in the straw stayed at a pressure equal to that in the beaker, which was 1 atmosphere. By creating a vacuum in the straw the pressure dropped enough to allow the liquid to be pushed into the straw by the atmospheric pressure. But this will only work if he does not allow air back into the straw, the inside must remain as a vacuum. Therefore he probably had to stop flow with his tongue in between sucking to close the tube off. I am guessing because 1 atmosphere is about 10 meters of water column, this experiment would not work with a straw longer than 10 meters (maybe 11, because he proved you can do an atmosphere of work above atmospheric pressure). We're going to need more juice though.

In the last, where you drank the juice, you were able to do it because you didn't have to do it one go, so you'd expand your lungs with the air in the hose, then let out the air through your nose. Is that why? The stuff about the underpressure and overpressure seems sort of confusing to me, right now. Anyways, great lecture, Prof!

Wow! Accidentally I came to your channel as I was searching teaching materials about magnetism. Found a long video of wonder of electricity and magnetism. I could not believe myself, how teaching science can be so interesting and lively , unbelievable, believe me professor. I postponed my dinner and completed the video. Now I am searching every topics that I prepare for teaching from your channel. May I use your video in my class?

Hi sir , my regards... now about the last demonstration : 1 st time you were able to create height difference of 1 meter as you were doing it in 1 breathe only.... and you exerted so high force by your lungs and that too in less time it was difficult for the body that's why it was just for a moment ...you were able to maintain that level for a moment..similarly while sucking ,you were trying to suck it in one breathe 2 nd time while sucking from 5 meter : every time you were sucking it in small steps ,sucking to small height in one breathe and then exhaling from nose..and during this time blocking the pipe with your tongue or anyhow by your mouth muscles and then again resuming from the same height and again sucking and repeating the same until it reach your mouth...and in each next breathe you have to use more strength of your muscles..as pressure difference was increasing step by step.. it means in 1 breathe we can create a pressure difference of 0.1 atm.... but doing so in continuous installments we can create more pressure difference depending on the strength of muscles of mouth and lungs...in some video on youtube a person could suck water up to around 7 meter.. also... sir ..in the end when you put the pipe out of your mouth ...to maintain it on same level you covered it with your thumb... to hold it on same height ...the same thing you were doing in the time between two breathes with your tongue or somehow by your mouth. SIR , is the explanation correct ...please tell me.. SIR I like your lectures very much..thank you Sir.

We can create a much higher under-pressure when sucking a drink through the straw because we are doing it through the gut, not through the lungs.

Walter Lewin is a legend, you can tell he really likes what he does

Physics is beautiful.. :)

Hi Prof. Lewin, hope you're keeping safe in Hawaii! Regarding the hydraulic jack, is it right for me to say that using Pascal's idea we are effectively able to "split" the work needed to lift a car up by say 10cm into multiple repetitions of muscular motion, so that mere humans can do so? That is to say, without such a machine is maybe quite impossible to lift the car with a single motion of human arms (since the power required is not feasible), but the jack breaks it down into managable loads (albeit at lower power i.e. much more "time" required than a single lift)?

Hallo Professor , I'm in highschool n well just really amazed how u'v managed to stand for hours , I wanted to ask where can I find a lecture on force due to water flow , also can u guide me where I can find lectures , as good as yours , IDK if they'll be but close to yours for biology and chemistry, although how great it'd been if u also taught these subjects as well, the world would've been a lot easier ✨

To give my students a feeling of the weight of air and the airpressure, I always used a ruler under a newspaper and gave the end of the ruler a great wack. It hurted but the faces of the students was worth it

Hey Professor Lewin! I enjoy all your lectures and am a big fan, but I think you misspoke at time 30:55 in the video, I think you meant to say that barometric pressure *difference* at a depth of 5m with respect to the surface of the liquid would be 1/2 atm, since actual pressure at a depth of 5m would be 1.5 atm. I understand that at depth of 900m, this difference of 1atm becomes negligible but nonetheless just wanted to point that out. Again a great lecture and I am blessed to watch these lectures during my lifetime!