8.01x - Module 22.02 - Angular momentum of a conical pendulum.

Conical Pendulum - Angular momentum depends on YOUR choice. Result is the same.

[@shook3487]

Thank you professor. I hope your health is good

[@VK-uv8jw]

I felt like I wanna quit college and spend that time watching ur videos

[@arpansarkar8901]

Best video to clear all doubts of conical pendulum

[@kavithakaruppanan7955]

NOW I AM WATCHING THIS IN 2020

[@simranjoharle4220]

Thank you Sir....this really helped!

[@sonorousgaming7202]

11:08 that what literally where my mind was not accepting that. thanks for the video

[@devayush10]

LOVED IT:)

[@arunbhardwaj2744]

professor, i have a similar question related to this,,that" i am rapping a light string of length l connected to a point mass m with its initial speed v ,, around my finger,,and i have to calculate increase in its speed when length of string becomes l/2",,,can i conserve the angular momentum here,,like we have did about point M,,i think no,, because as string is rapped around my finger its length is decreasing so the mass is also going upwards,,and its not moving in a particular horizontal circle,,then how can i calculate its increase in speed,, could u please give me a HINT.

[@fundamentalsofphysics8347]

wonderful explanation professor...

[@lecturesbywalterlewin.they9259]

:)

[@fundamentalsofphysics8347]

@@lecturesbywalterlewin.they9259 I wish i could meet you once in my life

[@dhananjaydixit9280]

I believe angular momentum is also conserved about the vertical z axis, right?

[@TheSpyFardin]

11:10 pm 29 May 2021! From Bangladesh 🇧🇩

[@KrishnaSharma-fx6kb]

Sir plz ask mit for more lectures like this of physics

[@shikharsrivastava3101]

thank you sir

[@mrb6172]

prof. i am sure u won't be seeing this comment on such a old video still if u see this, here is my question:- U showed us that the theta can never be 0 as gravity will oppose it but i see this from a different perspective Can i relate this one with the gyroscopic precession i mean to say that the pendulum is rotating with a angular acc. pointing upwards but then gravity is also pulling it downwards and i think the trajectory of gravity pulling it downwars is almost circular so it must have an angular acc. due to the rotation by gravity and so even if we have a very high angular momentum(also angular velocity) it must easily overcome gravity but since it is not negligible , gravity makes the pendulam spin with a max angle lower than 0 degree with the horiuzontal??? are my thoughts right sir?

[@klammer75]

how did he come to the w^2=g/Lcos(theta)...I can't seem to see how he derived that from the above 3 equations at the 3:00 mark. any help would be most appreciated, tku!

[@lecturesbywalterlewin.they9259]

+klammer75 You have to massage the equations as you learned in high school. Sorry. Please try again.

[@pedrocavalcanti46]

From the equation (3) you know that sin(t) = R/L. Now, go on the equation (2) and replace the result of the equation (3). Now you have: TR/L = m(w^2)R, work with it and get to: T = m(w^2)L, and I will call it equation (4). Now, the final step, replace the value for T that you found on (4) in (1), work with it until you get to what Lewin got. Sorry for the bad english.

[@agarshasuresh6244]

Could u pls teach current and electricity

[@lecturesbywalterlewin.they9259]

watch my 8.02 lectures

[@blee6117]

Hi Professor. How we can solve the same question if we remove gravity from question (if we do same experiment in space and change rope with thin sylindrical metal and attach a small ball(kg) to the edge it and rotate with lower angular velocity to catch the same θ as in question). Angular momentum will be still concerved according to P point? If No which external force or torque acting? Thanks.

[@lecturesbywalterlewin.they9259]

a conical pendulum does not work in the ISS as nothing has weight there bcoz the ISS is in free fall.

[@arunbhardwaj2744]

torque about point p is perpendicular to both horizontal and and vertical component of p but the direction of only horizontal component changes why?????

[@lecturesbywalterlewin.they9259]

bcoz of Newton - I can't help it

[@cricworld6797]

Excuse me professor I have a question for you .Here I eventualy came to a good understanding about this concequence .Yet I am bit puzzeled about the final segment .Here the Force "mg" is acting perpendiculer to the circuler parth .According to my knowlage it has no tangential component to the circuler path in order to give it a certain torque.Then how we can take mg to account??

[@lecturesbywalterlewin.they9259]

qustion unclear watch my 8.01 lectures

[@cricworld6797]

Thank you very much professor .I watched your 8.01 lectures .Early I was bit confused with the direction of the Tourqe .Now it's clear.Thank you very much sir.❤❤❤

[@heramb575]

At 10:08 professor shouldn't it be lmvsin(theta) as it is magnitude of a cross product?

[@lecturesbywalterlewin.they9259]

no

[@heramb575]

But why? I mean the cross product is defined to be as such isn't it?What am I missing here? If it is 'lmv' then u mean to say the angle between them is π/2?

[@lecturesbywalterlewin.they9259]

@@heramb575 the vector lower case L is perpendicular to the vector mv.

[@kasiviswanathboddeti9085]

@The Overlord imagine the plane containing both mv and l vector

[@jeebanmohanty4068]

Sir are your lectures are enough to crack jee advance which is held india.....

[@lecturesbywalterlewin.they9259]

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

[@atikshagarwal5147]

@@lecturesbywalterlewin.they9259 sir is legend . I hated physics till November but in 2 months the lectures by professor Lewin made me 💓 physics. Sir HCV sir is releasing a new book on electromagnetism.. Would love to see your opinion on it and it's comparison with Griffith...

[@jatinbhatt7826]

here you are proffesor :)

[@lecturesbywalterlewin.they9259]

what I said is correct, theta can be 89.9999 but not 90 degrees. I am surprised you did not get it. I show that w =>> infinity for theta => 90 degrees. An infinite angular frequency means an infinite rotational kinetic energy.

[@jatinbhatt7826]

+Lectures by Walter Lewin. They will make you ♥ Physics. yeah i got u professor but experimentally it is hard to show that 0.000001 degree gap. And actually it is difficult to demonstrate my student with that much accuracy. Some of them unable to accept this .

[@lecturesbywalterlewin.they9259]

the cos of 89.9 is 0.0017 that already pushing your luck

[@jatinbhatt7826]

+Lectures by Walter Lewin. They will make you ♥ Physics. oh my goodness. Thanks a lot professor. that's better explanation. Thanks a lot

[@RaviSingh-on2qr]

okay then think like this.... for the string to be balanced at any theta there should be a force acting upwards which will balance the weight of tha bob (which is genrally Tcos.theta), but for theta 90 degrees, this force vanishes & tension would only act radially. So no force would be there to balance the weight, thats why horizontal motion is impossible...

[@bhavukkalra1786]

professor i couldn't get the point.why angular momentum is conserved only about point m and not even anywhere on the z axis.could you please help.

[@lecturesbywalterlewin.they9259]

the torque relative to point m is zero. It's not zero relative to any other point.

[@arthur861020]

Dear Porf Lewin, can i ask what is the book you use in the course, i try to locate where i can find the examples and some reading material,thanks

[@lecturesbywalterlewin.they9259]

8.01PhysicsHans C. Ohanian2nd editionW.W. Norton & CompanyISBN 0-393-95748-9

[@arthur861020]

+Lectures by Walter Lewin. They will make you ♥ Physics. Thank you professor

[@raviraki7183]

At 13:45 why theta becomes alpha

[@raviraki7183]

Please explain sir i coudn't understand it

[@josephanderson7237]

What year was this recorded?

[@lecturesbywalterlewin.they9259]

probably 1996 +/- 1

[@agarshasuresh6244]

What are the books u use sir

[@lecturesbywalterlewin.they9259]

8.01 Physics Hans C. Ohanian Physics 2nd edition W.W. Norton & Company ISBN 0-393-95748-9 8.02 Physics for Scientists & Engineers by Douglas C. Giancoli. Prentice Hall Third Edition ISBN 0-13-021517-18 8.03 Vibrations and Waves by Anthony French CRC Press ISBN 9780748744473 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8

[@jhansilakshmi1380]

thank u sir