Hello Sir. I really hope you come across this message. You know, I was once an active follower of your channel and content...during the pandemic, when we were having lockdown , I would watch your MIT lectures daily. Then after 2022, I got busy with my life and pursuit of job. Today, while I was cleaning an old book shelf, I came across the book - For the Love of Physics, and suddenly I was reminded of you. I came back and watched your videos. It felt so refreshing. May you live longer and get healthier with each passing day. My warm regards for you Sir. With love, from India.
@@lecturesbywalterlewin.they9259 no Sir, you have always been and will always be with us..... the passion and eccentricity in your teaching is unique and it sparked the interest for Physics in me.... So, in students like me, you will always hold a special place in our memories...!!!!
thank you professor walter for sharing those I am from sri lanka,i really like your physics contents.your practical videos...no words,those are amazing. Your practical videos were more effective for me for the exams❤. literally i always watch ur videos
Aww...i keep following your videos.... This vintage video is so special...... Physics professors live their life with elegance...admiring the surroundings..... Physics professor from India
i love you professor always..........love from india........ in myclassroom we are discuss about you how you risked your life just for physics and your experiments
Dr Lewin, you mean when you were younger because you are still young :D. Thanks for the video. BTW, I didn't about NCAR's Walt Orr Roberts balloon engineering group till now. I collaborate with NCAR's lidar group here in Boulder. They do great science. Cheers. PS: No wonder Oppenheimer was able to teach himself Dutch in a month. I could almost understand it in the video. ;)
It's great to see your young memories❤.So much fun😍.Sir, Are you interested in Buddhist philosophy ? I can see a tiny Buddha statue behind you. That's why I am asking.
Sir, I have watched your 8.01x, 8.02x, 8.03x courses for neet, they are very good! I really appreciate making it available for everyone to see, thank you sir. But, sir, what do to about the chemistry part? Do you know any good courses for chemistry too, professor?
Respected Professor, Good Evening !! I go through your UA-cam lectures and video clips when I need to learn physics in a practical way. I was reading about the topic "Inertia". Inertia is the property of matter that resists changes in its state of motion or rest. What should be SI units for this term and what will be its dimensions? What type of physical quantity is this? Waiting for your reply Professor.
The SI unit for moment of inertia is kilogram meter squared (kg.m2). Moment of inertia is a quantitative measure of an object's rotational inertia or angular mass. It's the resistance that an object exhibits to changes in rotation around an axis. The distribution of mass in the body relative to the axis of rotation determines the moment of inertia.
You know what is "Moment of inertia" is - Or, do you not..❔ (Like for a helicopter rotor).🚁😊 Moment of inertia: I≝mR² [kg·m²] for a point particle or for a contiguous mass: I= ∫r²·δm=*= ∫r²·ρ·δV Where: ρ=ρ(r)=(δm/δV)ᵣ for some chosen coordinate system** with radius |r| in it. *(You can describe this with 3 nested integrals each with different coordinates.) **[Examples (for position vectors): Polar: r=(|r|, θ, z), Spherical: r=(|r|, θ, φ), Cartesian: r=(x, y, z)]
Walter Lewin, this are wonderful souvenirs. I remember also something from my youth. A poem, for MayDays. Can you guess the meaning ?. It is very very famous. Take care, always. I dont want to bore you always with poems. Tiefe Nacht LYNKEUS DER TÜRMER: Zum Sehen geboren, Zum Schauen bestellt, Dem Turme geschworen, Gefällt mir die Welt. Ich blick' in die Ferne, Ich seh' in der Näh' Den Mond und die Sterne, Den Wald und das Reh. So seh' ich in allen Die ewige Zier, Und wie mir's gefallen, Gefall' ich auch mir. Ihr glücklichen Augen, Was je ihr gesehn, Es sei wie es wolle, Es war doch so schön! Nicht allein mich zu ergetzen, Bin ich hier so hoch gestellt; Welch ein greuliches Entsetzen Droht mir aus der finstern Welt! Funkenblicke seh' ich sprühen Durch der Linden Doppelnacht, Immer stärker wühlt ein Glühen, Von der Zugluft angefacht. Ach! die innre Hütte lodert, Die bemoost und feucht gestanden; Schnelle Hülfe wird gefordert, Keine Rettung ist vorhanden. Ach! die guten alten Leute, Sonst so sorglich um das Feuer, Werden sie dem Qualm zur Beute! Welch ein schrecklich Abenteuer! Flamme flammet, rot in Gluten Steht das schwarze Moosgestelle; Retteten sich nur die Guten Aus der wildentbrannten Hölle! Züngelnd lichte Blitze steigen Zwischen Blättern, zwischen Zweigen; Äste dürr, die flackernd brennen, Glühen schnell und stürzen ein. Sollt ihr Augen dies erkennen! Muß ich so weitsichtig sein! Das Kapellchen bricht zusammen Von der Äste Sturz und Last. Schlängelnd sind, mit spitzen Flammen, Schon die Gipfel angefaßt. Bis zur Wurzel glühn die hohlen Stämme, purpurrot im Glühn.- Was sich sonst dem Blick empfohlen, Mit Jahrhunderten ist hin.
Maybe you can explain how the technik works in order to detect x-ray sources and their direction. When i take astro pictures, i need a stable goto mount and no vibrations. Today i uploaded a UA-cam Video on my channel from polar lights, Jupiter, Saturn, M45, M42, M13, mercury transit and much more recorded in Bochum Germany, where we have much light pollution.
For the Balloon payload we used NaI crystals. Scintillation crystals are used in detectors to convert X-rays or gamma rays into light pulses that are subsequently detected by either a Photomultiplier Tube (PMT) or a Silicon Photomultiplier (SiPM).
Thankyou for sharing it with us professor... ❤. Respected sir, I just like to be in contact with such teachers .. Though the only way to contact you is only through the youtube comment , I Guess😂... Just want to say keep uploading more and more videos sir, we'll happy to see your videos.. 😊 Thankyou sir. With regards, Your Indian Student😊
🖐sir, in the previous video, in my request about the help regarding my NEET 2025 exam preparations, you suggested your 8.01, 8.02 and 8.03 courses' lectures. but the NEET physics syllabus also includes thermodynamics, mechanical properties of solids and fluids, thermal properties of matter .... what can i do for preparing those topics sir?..and an another request, how can i get the PDFs of the books that you used in each courses?..i find difficult to download then from the internet :( .....hope you will respond to my request :)
Hello sir, I have just passed my 10th grade at school and i want study physics, but i don't really know anything about physics except things i learned at school. So can watching your lectures help me in any way?? If no then from where should i start?
my lecture notes are stored at my home in folders - Each folder holds 3 lectures - about 50 pages per lecture thus 150 pages per folder => 1800 pages for 8.01 and 8.02 and for 8.03. A special book case was made for them. The wait for one folder (3 lectures) is about 3 kg; thus 40 kg for 8.01 and for 8.02 and for 8.03.
@@lecturesbywalterlewin.they9259Wow! If you could get someone to scan them you could turn it into an e-book of some sort. I'm sure that many people will buy something like that given the popularity of your lectures. If you do go ahead with something like that, you'll want some kind of menu and reference system to go along with it. - Maybe AI-based? 🤔 I think there is a need for something more accessible and accurate than wiki and so on. There are currently limits to online physics because of the lack of experts who bother to edit articles, and so there must be a lot of mistakes out there. I find that AI is getting better and better at cross-referencing physics principles, but it's still so-so when it comes to solving actual problems and applying relevant mathematics, so I think that human physicists will still be required for the foreseeable future.
Hi, Really I'm The fan of Physics but wasn't enjoying it in the way of school does but When I saw your Lecture it's the " Real Physics" I have experienced through you.. Was amazing 👏... People believe that Physics is 80% Math but In reality Physics has only 10% Math or even less .. when it is taught as Physics... Sir don't you think about the "Creator of the Universe "that created huge and massive Universe and Super Intelligent Human ? Don't you think The creator of the Universe created the Universe and forgot to give the purpose of life ?? What about life after death?? Does God sent the guide ,have we researched about it or it is written by Humans?? Then atleast one should be true ?? Have we looked into it ?? If it is true then it must be most preserved and most updated and cannot be old ,No one should be able to change or update. It must confirm that it is from God for ex, for today this era is of "science and technology " Whatever sir I request you to look into the matter search for what is the true purpose of life and it cannot be decided by humans... We don't know when we are going to die ....
Hi my dear professor its me again Okey ! Now I understand how you see the story، it make sense so that you see that Quran is fault am l right? But there is another possibility just like in the Second degree equation It seems like there is two facts and one demonstrate the creator and the other didn't but Let's thinks deeper in the Quran and forget about the evolution theory for a while The verse mentioned two different types of sciences and they absolute right facts and only the creator can did it Let see the another Scientific miracle Physic in surah the star ( By the star when it sets) Described a black hole medicine The saying and the teaching of prophet that he always sleeps on his right side of his body and that best way to sleep One of the Linguist said he never saw something like Quran and it from God indeed because humans always carries Language more than it can to express feelings what is that mean Like if you have been waiting for long time for some openings the door for you you will say to him I have been waiting for hours and that's not true these fault Accompanied by human nature and didn't find it in Quran and there are more and more and more of these Scientific miracle that's just one of it enough to prove the creator
@@lecturesbywalterlewin.they9259 I don't know why they are trying to convert you professor! They can't mind their own business. Freedom of religion is given to all individuals. Our beloved professor is an atheist, kindly let him be!
@@lecturesbywalterlewin.they9259 You did a lecture on a related topic. 8.01 lect 24. Also, I found this MIT lecture by somebody else: ua-cam.com/video/OlQie93CwLY/v-deo.htmlsi=pFTuo4ta0DpuHPwl
@@lecturesbywalterlewin.they9259 Example problem for you: A helicopter rotor blade can be considered approximately as a long thin rod. Consider a helicopter with 3 main blades attached to the same axis, arranged symmetrically, each 5.2m long with mass m=160kg. Calculate: (a) the moment of inertia of the 3 blades about the axis of rotation (b) the torque needed from the motor to achieve a speed of 5 rev/s in 8s. (c) the energy needed to bring the blades from rest to a speed of 5 rev/s (d) the required power of the helicopter engine to maintain 5 rev/s. Part 2: A helicopter is attempting to clear a hill in front of it with a 30° upwards slope. It's mass including payload is M= 2000kg. The mass of each of its 3 blades is 160kg. Each blade is 5.2m long and is connected to one common axis. Calculate (a) the moment of inertia of each blade. (b) the torque required if the rotors begin at rest and then revolve at 5 rev/s within 8s (c) energy of the rotors required to go from rest to 5 rev/s (d) power required from the motor to achieve 5 revs/s. It starts off level at 0° to the horizon at an altitude of 2000m above sea level and travels 100m at 12.5 m/s. At the start position, the height above the base of the hill is 50m. Gravity in this region can be assumed constant at about g=9.79 m/s. Taking account of an air density ρ at 2000m, which is about 1.1 kg/m³: 1. For the angles of attack (i) θ=0° (ii) θ=30° , recalculate (a) to (d), but with constant forward motion along its trajectory instead of just stationary hovering, assuming instead that each blade has a symmetric aerofoil cross-section, consisting of an isosceles triangle with 2 side lengths of 33cm, attached to half-circles of radii 10cm. 2. Calculate the max lift achieved and drag of the helicopter, as it progresses to the top of the hill for both cases (i) and (ii). (Assume the frontal & top body cross-sections are circles of radius 1.5m, main body is spherical & copter tail protruding from the center of the main body is a cylinder 5m long, 0.5m wide) 3. If it normally takes 8s to reach the hilltop, along a straight trajectory, what is the minimum rotor-speed required to achieve this or better in rev/s ?
@@lecturesbywalterlewin.they9259 You can go ahead and use my problem (or modify it) if you like. I think some people need to learn more about helicopters. 😊
Hello Sir. I really hope you come across this message. You know, I was once an active follower of your channel and content...during the pandemic, when we were having lockdown , I would watch your MIT lectures daily. Then after 2022, I got busy with my life and pursuit of job.
Today, while I was cleaning an old book shelf, I came across the book - For the Love of Physics, and suddenly I was reminded of you. I came back and watched your videos. It felt so refreshing. May you live longer and get healthier with each passing day. My warm regards for you Sir.
With love, from India.
thanks
Wow, Lovely! Thanks for Sharing Professor ♥️
My pleasure!
The soul never ages, only improves. That's is why we stills see the young Lewin in the older version, because your essence hasn't changed
I am 88 yr old - my days are numbered
@@lecturesbywalterlewin.they9259
Speak for yourselves. I intend to live forever by programming various AIs with my award winning personality. 🏆😊
@@lecturesbywalterlewin.they9259 no Sir, you have always been and will always be with us..... the passion and eccentricity in your teaching is unique and it sparked the interest for Physics in me.... So, in students like me, you will always hold a special place in our memories...!!!!
May sir you live more so that I can continue watching your great videos regards sir and much love @@lecturesbywalterlewin.they9259
Don't say like that😢 we not able to miss you
Professor, welcome to your lectures. 😊😊
Sir I am from India and study in class 11 and sir me and my friends really love your videos and also love you ❤❤
Great 👍
When I see your video then I supposed that I was there
Love you sir❤
You are a genius sir.
I have gotten many many knowledges from your lectures video.
I want to learn more...
Thank you so much sir.
Those vintage cars ❤ remind of a bygone era
thank you professor walter for sharing those
I am from sri lanka,i really like your physics contents.your practical videos...no words,those are amazing.
Your practical videos were more effective for me for the exams❤.
literally i always watch ur videos
great
Awesome video sir it gives a different vibe and I wonder what is the language they are talking in the video.
Aww...i keep following your videos.... This vintage video is so special...... Physics professors live their life with elegance...admiring the surroundings.....
Physics professor from India
Film has such a way of brining back memories.
so beautiful sir
Seeing ourselves as young is so sad but we have to move on as time can't be reversed 😢
Yep, memories. I know the feeling. Thank you my friend.
Love this video
i love you professor always..........love from india........ in myclassroom we are discuss about you how you risked your life just for physics and your experiments
Sir is still young in his 80s 😊 with a long life to live
Thanks professor, your lectures are great I cracked competitive exam 😇
THANKYOU PROFESSOR ! FOR ALL OF YOUR LECTURES ! 🥹
You are very welcome
Wow Sir So Nice Vintage ❤🎉😊
Legend is getting older😢
Sir you are great👍👏
Great piece of yesteryear. I enjoy looking at the old vehicles and equipment. Would have been great if you narrated it. I enjoy a good story.
Beste meester ter wereld. Prachtige video's!❤
Nice video sir☺️
Thanks sir 🙏 ❤❤ for sharing to us
It's my pleasure
Love you sir u made me love for physics
I love you so much Sir❤❤❤❤❤❤❤❤❤❤
Hi walter Lewin sir yours big fan from ind
Dr Lewin, you mean when you were younger because you are still young :D. Thanks for the video. BTW, I didn't about NCAR's Walt Orr Roberts balloon engineering group till now. I collaborate with NCAR's lidar group here in Boulder. They do great science. Cheers. PS: No wonder Oppenheimer was able to teach himself Dutch in a month. I could almost understand it in the video. ;)
I watched to the end. It's truly fascinating...
I'm curious, why did you tear up?
Cool
It's great to see your young memories❤.So much fun😍.Sir, Are you interested in Buddhist philosophy ? I can see a tiny Buddha statue behind you. That's why I am asking.
♥️✊🏻🔥
Sir, I have watched your 8.01x, 8.02x, 8.03x courses for neet, they are very good! I really appreciate making it available for everyone to see, thank you sir. But, sir, what do to about the chemistry part? Do you know any good courses for chemistry too, professor?
Want to meet you in MIT sir ❤
Respected Professor,
Good Evening !!
I go through your UA-cam lectures and video clips when I need to learn physics in a practical way.
I was reading about the topic "Inertia".
Inertia is the property of matter that resists changes in its state of motion or rest.
What should be SI units for this term and what will be its dimensions?
What type of physical quantity is this?
Waiting for your reply Professor.
The SI unit for moment of inertia is kilogram meter squared (kg.m2). Moment of inertia is a quantitative measure of an object's rotational inertia or angular mass. It's the resistance that an object exhibits to changes in rotation around an axis. The distribution of mass in the body relative to the axis of rotation determines the moment of inertia.
@@lecturesbywalterlewin.they9259 Sir, Is Inertia and Moment of Inertia have same si units, dimensions and nature???
You know what is "Moment of inertia" is
- Or, do you not..❔
(Like for a helicopter rotor).🚁😊
Moment of inertia: I≝mR² [kg·m²] for a point particle or for a contiguous mass:
I= ∫r²·δm=*= ∫r²·ρ·δV
Where: ρ=ρ(r)=(δm/δV)ᵣ for some chosen coordinate system** with radius |r| in it.
*(You can describe this with 3 nested integrals each with different coordinates.)
**[Examples (for position vectors):
Polar: r=(|r|, θ, z),
Spherical: r=(|r|, θ, φ),
Cartesian: r=(x, y, z)]
Walter Lewin, this are wonderful souvenirs. I remember also something from my youth. A poem, for MayDays. Can you guess the meaning ?. It is very very famous. Take care, always. I dont want to bore you always with poems.
Tiefe Nacht
LYNKEUS DER TÜRMER:
Zum Sehen geboren,
Zum Schauen bestellt,
Dem Turme geschworen,
Gefällt mir die Welt.
Ich blick' in die Ferne,
Ich seh' in der Näh'
Den Mond und die Sterne,
Den Wald und das Reh.
So seh' ich in allen
Die ewige Zier,
Und wie mir's gefallen,
Gefall' ich auch mir.
Ihr glücklichen Augen,
Was je ihr gesehn,
Es sei wie es wolle,
Es war doch so schön!
Nicht allein mich zu ergetzen,
Bin ich hier so hoch gestellt;
Welch ein greuliches Entsetzen
Droht mir aus der finstern Welt!
Funkenblicke seh' ich sprühen
Durch der Linden Doppelnacht,
Immer stärker wühlt ein Glühen,
Von der Zugluft angefacht.
Ach! die innre Hütte lodert,
Die bemoost und feucht gestanden;
Schnelle Hülfe wird gefordert,
Keine Rettung ist vorhanden.
Ach! die guten alten Leute,
Sonst so sorglich um das Feuer,
Werden sie dem Qualm zur Beute!
Welch ein schrecklich Abenteuer!
Flamme flammet, rot in Gluten
Steht das schwarze Moosgestelle;
Retteten sich nur die Guten
Aus der wildentbrannten Hölle!
Züngelnd lichte Blitze steigen
Zwischen Blättern, zwischen Zweigen;
Äste dürr, die flackernd brennen,
Glühen schnell und stürzen ein.
Sollt ihr Augen dies erkennen!
Muß ich so weitsichtig sein!
Das Kapellchen bricht zusammen
Von der Äste Sturz und Last.
Schlängelnd sind, mit spitzen Flammen,
Schon die Gipfel angefaßt.
Bis zur Wurzel glühn die hohlen
Stämme, purpurrot im Glühn.-
Was sich sonst dem Blick empfohlen,
Mit Jahrhunderten ist hin.
Hello genius
Maybe you can explain how the technik works in order to detect x-ray sources and their direction. When i take astro pictures, i need a stable goto mount and no vibrations. Today i uploaded a UA-cam Video on my channel from polar lights, Jupiter, Saturn, M45, M42, M13, mercury transit and much more recorded in Bochum Germany, where we have much light pollution.
For the Balloon payload we used NaI crystals. Scintillation crystals are used in detectors to convert X-rays or gamma rays into light pulses that are subsequently detected by either a Photomultiplier Tube (PMT) or a Silicon Photomultiplier (SiPM).
Heel bijzonder dat het dunne plastic een kleine 2300kg kan houden zonder te scheuren, buiten de eerste keer om. Maar super toffe video om te zien!
How Can I go mit ❤
apply
🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉
Thankyou for sharing it with us professor... ❤. Respected sir, I just like to be in contact with such teachers .. Though the only way to contact you is only through the youtube comment , I Guess😂...
Just want to say keep uploading more and more videos sir, we'll happy to see your videos.. 😊
Thankyou sir.
With regards,
Your Indian Student😊
It's my pleasure
🖐sir, in the previous video, in my request about the help regarding my NEET 2025 exam preparations, you suggested your 8.01, 8.02 and 8.03 courses' lectures. but the NEET physics syllabus also includes thermodynamics, mechanical properties of solids and fluids, thermal properties of matter .... what can i do for preparing those topics sir?..and an another request, how can i get the PDFs of the books that you used in each courses?..i find difficult to download then from the internet :( .....hope you will respond to my request :)
all I can offer you are my 95 MIT course lecturess + about 600 problems
@@lecturesbywalterlewin.they9259 thank you sir, I will be glad for you help❤❤
Hello sir,
I have just passed my 10th grade at school and i want study physics, but i don't really know anything about physics except things i learned at school.
So can watching your lectures help me in any way??
If no then from where should i start?
my lectures require knoweledge of calculus
@@lecturesbywalterlewin.they9259 It means I have got a long way to go.
Professor ...
You have blackboard pictures of your lectures .....
If possible pls share them .
they are already on my 95 MIT lectures. You can copy them.
Good afternoon sir
Sir may i get your Blackboard Lecture notes pdf
( What you wrote on BlackBoard while explaining )
Thanks sir
my lecture notes are stored at my home in folders - Each folder holds 3 lectures - about 50 pages per lecture thus 150 pages per folder => 1800 pages for 8.01 and 8.02 and for 8.03. A special book case was made for them. The wait for one folder (3 lectures) is about 3 kg; thus 40 kg for 8.01 and for 8.02 and for 8.03.
@@lecturesbywalterlewin.they9259Wow!
If you could get someone to scan them you could turn it into an e-book of some sort.
I'm sure that many people will buy something like that given the popularity of your lectures.
If you do go ahead with something like that, you'll want some kind of menu and reference system to go along with it.
- Maybe AI-based? 🤔
I think there is a need for something more accessible and accurate than wiki and so on.
There are currently limits to online physics because of the lack of experts who bother to edit articles, and so there must be a lot of mistakes out there.
I find that AI is getting better and better at cross-referencing physics principles, but it's still so-so when it comes to solving actual problems and applying relevant mathematics, so I think that human physicists will still be required for the foreseeable future.
Hi, Really I'm The fan of Physics but wasn't enjoying it in the way of school does but When I saw your Lecture it's the " Real Physics" I have experienced through you..
Was amazing 👏...
People believe that Physics is 80% Math but
In reality Physics has only 10% Math or even less .. when it is taught as Physics...
Sir don't you think about the "Creator of the Universe "that created huge and massive Universe and Super Intelligent Human ?
Don't you think The creator of the Universe created the Universe and forgot to give the purpose of life ??
What about life after death??
Does God sent the guide ,have we researched about it or it is written by Humans??
Then atleast one should be true ??
Have we looked into it ??
If it is true then it must be most preserved and most updated and cannot be old ,No one should be able to change or update.
It must confirm that it is from God for ex,
for today this era is of "science and technology "
Whatever sir I request you to look into the matter search for what is the true purpose of life and it cannot be decided by humans...
We don't know when we are going to die ....
I respect what you believe in - I trust you also respect that I am an atheist
Hi my dear professor its me again
Okey ! Now I understand how you see the story، it make sense so that you see that Quran is fault am l right?
But there is another possibility just like in the Second degree equation
It seems like there is two facts and one demonstrate the creator and the other didn't but Let's thinks deeper in the Quran and forget about the evolution theory for a while
The verse mentioned two different types of sciences and they absolute right facts and only the creator can did it
Let see the another Scientific miracle
Physic in surah the star
( By the star when it sets) Described a black hole
medicine
The saying and the teaching of prophet that he always sleeps on his right side of his body and that best way to sleep
One of the Linguist said he never saw something like Quran and it from God indeed because humans always carries Language more than it can to express feelings what is that mean
Like if you have been waiting for long time for some openings the door for you you will say to him I have been waiting for hours and that's not true these fault Accompanied by human nature and didn't find it in Quran and there are more and more and more of these Scientific miracle that's just one of it enough to prove the creator
I respect what you believe in - I trust that you also respect that I am an atheist
@@lecturesbywalterlewin.they9259 thanks for your time 🌺🌻
@@lecturesbywalterlewin.they9259 I don't know why they are trying to convert you professor! They can't mind their own business. Freedom of religion is given to all individuals. Our beloved professor is an atheist, kindly let him be!
Have you got any problems about helicopters❔
(Asking for a "friend"). 🏔️🚁😊
I do not rember - there are more than 350 problems on my channel.
@@lecturesbywalterlewin.they9259 You did a lecture on a related topic. 8.01 lect 24.
Also, I found this MIT lecture by somebody else: ua-cam.com/video/OlQie93CwLY/v-deo.htmlsi=pFTuo4ta0DpuHPwl
@@lecturesbywalterlewin.they9259
Example problem for you:
A helicopter rotor blade can be considered approximately as a long thin rod. Consider a helicopter with 3 main blades attached to the same axis, arranged symmetrically, each 5.2m long with mass m=160kg.
Calculate:
(a) the moment of inertia of the 3 blades about the axis of rotation
(b) the torque needed from the motor to achieve a speed of 5 rev/s in 8s.
(c) the energy needed to bring the blades from rest to a speed of 5 rev/s
(d) the required power of the helicopter engine to maintain 5 rev/s.
Part 2:
A helicopter is attempting to clear a hill in front of it with a 30° upwards slope.
It's mass including payload is M= 2000kg. The mass of each of its 3 blades is 160kg. Each blade is 5.2m long and is connected to one common axis. Calculate (a) the moment of inertia of each blade. (b) the torque required if the rotors begin at rest and then revolve at 5 rev/s within 8s (c) energy of the rotors required to go from rest to 5 rev/s
(d) power required from the motor to achieve 5 revs/s.
It starts off level at 0° to the horizon at an altitude of 2000m above sea level and travels 100m at 12.5 m/s. At the start position, the height above the base of the hill is 50m.
Gravity in this region can be assumed constant at about g=9.79 m/s.
Taking account of an air density ρ at 2000m, which is about 1.1 kg/m³:
1. For the angles of attack (i) θ=0° (ii) θ=30° , recalculate (a) to (d), but with constant forward motion along its trajectory instead of just stationary hovering, assuming instead that each blade has a symmetric aerofoil cross-section, consisting of an isosceles triangle with 2 side lengths of 33cm, attached to half-circles of radii 10cm.
2. Calculate the max lift achieved and drag of the helicopter, as it progresses to the top of the hill for both cases (i) and (ii).
(Assume the frontal & top body cross-sections are circles of radius 1.5m, main body is spherical & copter tail protruding from the center of the main body is a cylinder 5m long, 0.5m wide)
3. If it normally takes 8s to reach the hilltop, along a straight trajectory, what is the minimum rotor-speed required to achieve this or better in rev/s ?
@@lecturesbywalterlewin.they9259 You can go ahead and use my problem (or modify it) if you like.
I think some people need to learn more about helicopters. 😊