Class 11 Physics | Rigid Body Dynamics | #23 Angular Momentum | For JEE & NEET

PG Concept Video | Rigid Body Dynamics | Angular Momentum by Ashish Arora
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[@arodot5463]

5:46 This is the first time I have seen Ashish sir leave his pen.

[@MemeConnoisseur]

No bro whenever Sir teaches applications of cross product he leaves his pen

[@steak2654]

@@MemeConnoisseur Do you understand the meaning of "first time *i have seen* " ?

[@madugulathriloknath9789]

Highly useful quick revision of concepts

[@hermionegranger8833]

not only for revision but also for first time learning of concepts..if watched in proper sequence..

[@chakradhar5884]

@@hermionegranger8833 yes

[@ojasdeshpande7296]

@@hermionegranger8833 which class?

[@nishadraj9972]

@@hermionegranger8833 Yes

[@omkondawar5899]

App sabhi log konsi IIT pahuche😊??

[@ayushKumar-mk1lk]

Very helpful...for quick revision and analysis....Lots of thanks to ashish sir.....

[@anitatiwari6425]

This is very useful for understanding jee advance 2016 question

[@ascyrax8507]

Case 4- whenever such a question comes , then can i take L due to rotation w.r.t any pt similar to P, directly as ((Ic.o.m)*w) ??

[@shardulkhare4861]

Sir,shouldnt we take shortest distance of line of motion from the point p? as in case 1?

[@jyotsnamadhavi6203]

In DC Pandey (book),about case(3), It is given that the direction of angular momentum is in the direction of angular velocity , only if, the body is exactly symmetrical about the axis of rotation otherwise the direction is different...why is that?

[@physicsgalaxyworld]

If body is symmetrical about AOR the horizontal components of all angular momenta will get cancelled out... so the part left is along the axis in the direction of AOR whereas in non symmeteric bodies the component of angular momenta in direction normal to AOR will be non-zero.

[@the_truth_of_society]

@@physicsgalaxyworld but i think L=Iw is always true for 2D bodies...bcz in that case every particle is doing circular motion and for each particle direction of angular momemtum is always upward or downward...depending upon in which direction body is rotating

[@tpsicmin]

Thank You Sir❤❤❤❤❤

[@kartiknarayansahoo3260]

Sir in case-1, won't the angle be 180-theta between vectors v and r(acc. to arrow heads)? Thank you.

[@physicsgalaxyworld]

yes thats right but we are using sin(180° - Θ) = sinΘ

[@kartiknarayansahoo3260]

@@physicsgalaxyworld okay.. thank you, sir.

[@shivanshikasahani6465]

Thank u so much sir 🙏😊

[@songlyricsyoutube9471]

Sir, if I were to calculate total angular momentum of a rigid body having angular momentum W and linear velocity equal to Omega * Radius, then the total angular momentum would just be I * W right? We will not consider linear momentum since this is only a pure rotational motion because linear velocity equals Omega * Radius. Am I right?

[@physicsgalaxyworld]

For a rigid body in rotation you can define linear velocity only for one point as all points of body have different linear velocities... so there is no point of talking linear velocity of the body...

[@KaranDoshicool]

Is case 4 valid for a point on the body?

[@lm10sanjay37]

Sir you are great👍

[@Mr.Tapori]

Same question asked in 2016 jee advanced ❤

[@himanshu5891]

In a book, it is written that if axis of rotation passes through COM then even if it is accelerating still torque of pseudo force about that axis is zero. Why?

[@umasrikanukollu7144]

Sir please send me the link of the video in case when the axis is not passing through centre of mass but translating and rotating please thank you in advance

[@umasrikanukollu7144]

Really helpful thank you sir

[@yashpandey9550]

but the topic of case 4 for angular momentum is "Angular momentum of a rotating body about an AOR passing through COM and moving translationally" ! But thats city confusing as you said that we are calculating L about point p ???

[@physicsgalaxyworld]

+Yash Pandey I have given the expression not derived it here thats why you might be confusing about it... you can also derive it by considering an element of mass dm in body and find it by vector sum of velocities of element, you will get the same result... but the derivation may not be useful in the cases we will deal for any of the advances cases so I haven't taken it... and remember you will be able to use this result only for the body which is rotating about com and axis is in translation motion... otherwise L will change with time...(this is also not in scope of this level)

[@yashpandey9550]

So "I" which is used in the result is the moment of inertia of the body about the AOR passing through COM and not through point P ?

[@hydraalister9708]

Yash Pandey

[@raaggeesingh1638]

10:56 sir is it possible to find the angle of Lmp and PC

[@hellot5166]

sir i think the translational ang momentum in case 4 is negative wrt to the rotational angular momentum

[@vandanavyas7697]

Sir, At the end of the video you told to make another video about the advance cases of angular momentum in which the body is rotating about AOR not passing through COM.

[@physicsgalaxyworld]

such cases are not in scope of these lectures and not in any competitive examinations... and as of now advance level university classes are on hold and not released yet...

[@vandanavyas7697]

Sir, when will they be released?

[@sejalpandey3862]

5:45 sir why we didn't take sintheta with r vector

[@songlyricsyoutube9471]

I*W is the angular momentum of the body with respect to the rotating axis, but we were supposed to find it with respect to the point P, so why have we not take the angular momentum of the rigid body with respect to point P?

[@physicsgalaxyworld]

angular speed is same in all frames...

[@songlyricsyoutube9471]

Sir, please reply to my other question also on this video. I am satisfied with this answer.

[@mattmcguire5350]

Physics Galaxy sir then I (moment of inertia) is about which point (point P or about center of mass of rigid body)?

[@alphaiitd1]

Thanks sir

[@pranavbhalerao8574]

Sir aapki offline classes ki video bhi ek bar upload kar do pls Jin jin ko dekha hai vo like kare

[@mayanktripathi3470]

Sir I have a doubt In case 4 why we have taken Lt about center of axis and Lc about point P.

[@physicsgalaxyworld]

I have written it directly but you can get the result by considering an elemental mass dm inside the body and integrate the result for this elemental mass about point P

[@bios546]

for a charged particle... is the magnetic field of the particle anti parallel to the angular momentum ?

[@physicsgalaxyworld]

Not necessary, it depends upon its charge polarity...

[@bios546]

o! that's true! thanks sir!

[@anshjain257]

in which video linear momentum and moment is discussed?????

[@physicsgalaxyworld]

There are many videos... it will be better for you to watch our videos in sequence on our website at www.physicsgalaxy.com

[@lostNseeker]

Why there is a need to defined by help of point or axis..... If we compare with linear momentum atleast 3 bodies are required( 1st , 2nd and observer) and then only we can give relative velocities.....but here the concept of defining by point and not by refranced frame is actually confusing me sir.....plz help

[@DrakeRing]

Thank you, I came for Case 4

[@n.h.9691]

In 9.40 can we use R' = R ? Coz shortest distance

[@himanshu5891]

In case 4 , the expression of Lc is I(omega) where I is moment of inertia of COM. But in the case of Instantaneous axis of rotation in pure rolling, when we write momentum equation we take I to be Moment of inertia about IAOR not COM. Why?

[@ariahito-hu6rp]

Sir can you sent link of booster classes

[@shivamverma9447]

Bhai booster classes mili kya?

[@shyamsundarmishra2553]

Haa

[@pranviaggarwal5165]

@@shyamsundarmishra2553 can u pl tell where did u find

[@vaibhaviloveu]

Sir. Can a body have angular momentum in a direction different from angular velocity for a rigid body rotating about a fixed axis

[@7_thala_for_a_reason]

no and never

[@vandanavyas7697]

Sir, in the formula L=IW , you told that here 'I' is treated as scalar quantity. So it is originally a vector quantity that we treat as a scalar in this case or it is just a scalar quantity ???

[@physicsgalaxyworld]

No... it is already discussed that Moment of Inertia is a tensor quantity but tensors are not in our scope of coverage so for a given axis of rotation we always consider MI as a scalar quantity for calculation...

[@vandanavyas7697]

Sir Are tensors in the JEE course?

[@ManojDas-ge8zj]

sir in case II if we have to calculate the angular momentum of the particle about an imaginary axis of rotation parallel to the original axis of rotation what will be the expression in that case? we can find out I of the continuous body using parallel axis theorem but what about angular velocity

[@physicsgalaxyworld]

Not in scope of these lectures... and not useful for you also... This can only be done if body is actually rotating about its com and moving translationally as given in case IV...

[@ManojDas-ge8zj]

is this beyond scope of jee advanced?

[@HarshvardhanNigam11]

sir how do we decide whether r*v or v*r in first case . got a bit confused .

[@SaiTeja-oo3dv]

Harshvardhan Nigam I have seen u in every video of physics galaxy...good

[@HarshvardhanNigam11]

Sai Teja :)

[@physicsgalaxyworld]

Its always r x v in angular momentum... direction can be found by right hand thumb rule also...

[@HarshvardhanNigam11]

Physics Galaxy ok sir got it . tnx

[@shubhammittal7013]

@@anmolempire1197 you tell your results

[@ascyrax8507]

Sir , in case 4 - L due to rotation and L due to translation seem to be in opposite direction..so shouldn't we be finding their difference??plz correct me if i am wrong

[@saayanbiswas209]

They have used vector notation When you put the magnitudes they do substract

[@divitgoyal5901]

sir in case 2 and 3 you are taking pts about which angular momentum has to be calculated on AOR only is it compulsory. Or we can take it anywhere.

[@physicsgalaxyworld]

AOR about which angular momentum is being calculated can be considered anywhere...

[@divitgoyal5901]

Physics Galaxy sir but in 4th case you have taken AOR somewhere and point aboot which angular momentum is being calculated elsewhere.

[@physicsgalaxyworld]

Angular momentum can be calculated about any point in space... it is not necessarily located on AOR... and for a body its AOR can also be located anywhere about which angular momentum can be calculated...

[@divitgoyal5901]

Physics Galaxy sir if in case 2 we take point p somewhere else and not on AOR then will there be difference in the result we have got??There should be I guess .

[@saicharanreddy1053]

sir I should be about AOR which is at P

[@priyanksoni4745]

sir is there any video of yours on how to calculate torque I couldn't find it on KZbin

[@physicsgalaxyworld]

Torque calculation is there in many examples and illustrations of rigid body dynamics... you can watch these...

[@ajeet3259]

Sir how to decide the order of r and v. Why r x v and not v x r?

[@physicsgalaxyworld]

cross product in any relation is defined as per the correct direction of the physical quantity... if you take v x r then direction will be opposite to that given by right hand thumb rule for angular physical quantities...

[@Ejaznaj]

Sir how do we know correct direction to confirm r×v

[@danielbaker7464]

Is moment of inertia a scalar or a vector? Also is angular displacement a vector?

[@gigachad6844]

Daniel Baker Are you in kindergarten?

[@viraj1304]

Bruh💀 You should start Physics from Basic Mathematical tools I guess

[@SheryanKumar]

Hi, moment of inertia is a tensor quantity, but since tensors are not in JEE syllabus, we are taking it as a scalar. Yes, angular displacement is a vector

[@vandanavyas7697]

Sir, why you wrote L= m(r×v) and why not L=m(v×r).

[@physicsgalaxyworld]

Because thats the way angular momentum is defined... for proper direction of vector...

[@pratikpiyush2540]

sir how to go through all booster classes as i am not able to find it anywhere. when i searched it on google then there are only 2 to 3 videos. Sir please tell where and how to see booster class. Sir i am huge fan of your teaching. Please specify sir.

[@physicsgalaxyworld]

download our PG LIVE mobile app... and see the schedule of booster classes going to be streamed...

[@pratikpiyush2540]

sir I downloaded it. And now I can see the schedule. Sir can you tell me the difference between booster classes and fundamental classes in there? And sir is there any chance to see the videos which were scheduled at a previous date.

[@physicsgalaxyworld]

previously scheduled videos will be restreamed again after two weeks... and fundamental classes cover every elemental aspect of the topic whereas booster classes requires the viewer to have fundamental idea...

[@pratikpiyush2540]

thank you sir

[@mamtagupta6048]

@@pratikpiyush2540 how you download it ,it is not showing in play store

[@rajnisingh3410]

Sir can u please tell me the link of video in which torque is explained

[@physicsgalaxyworld]

torque is separately not explained any video... we used its applications... it is simply turning effect of a force... which can be calculated by product of force magnitude with the perpendicular distance of line of action of force to the point about which torque is calculated...

[@rajnisingh3410]

@@physicsgalaxyworld thank u so much for the reference

[@Trax2551]

Sir I am not getting the videos of booster classes for this chapter.

[@dynamo7731]

Sir you did not teach torque force

[@arvindgupta4129]

Sir should we totally dependent on your videos for JEE preparation or go further anywhere for learning concept to clear concept and so on?????......... Bcoz I am preparing for jee from u tube and for physics should we do it???????

[@arvindgupta4129]

Sir but I'm sure for numerical approach we should totally dependent.......

[@physicsgalaxyworld]

along with videos if you use our 'Physics Galaxy' 2e series of books then nothing else is required for learning as well as for practice...

[@arvindgupta4129]

Sir I am using Allen institute 's module........ And dlp as well........so sir is Okkk??????

[@physicsgalaxyworld]

@@arvindgupta4129 Thats ok and sufficient...

[@arvindgupta4129]

Thanks sir

[@kusumakumari6635]

Sir,Are these videos enough for JEE preparation? I couldn't find some topics in these videos

[@physicsgalaxyworld]

Yes... which topics you are looking for ?

[@kusumakumari6635]

@@physicsgalaxyworld topics like instantaneous axis of rotation, torque,vandegraff generator,cyclotron and centre of gravity

[@physicsgalaxyworld]

all these (except torque) are covered in booster classes... torque is a basic theoretical concept covered at early class level and calculated as moment of applied force...

[@kusumakumari6635]

@@physicsgalaxyworld Thank you sir

[@arnavvishal3426]

@@physicsgalaxyworld where to find your booster classes sir?

[@yashpandey9550]

In this equation the moment of inertia is about point "P" i guess ??

[@physicsgalaxyworld]

+Yash Pandey No its about the axis of rotation.... we are calculating Lc which is about com of body...

[@sherlockamir7732]

sir...how does the top goes round and..round without falling down... although mg is the only acting force...?

[@physicsgalaxyworld]

No the point where the body is hinged on the axis of rotation, it is also exerting an external force which is responsible for its stable rotational motion...

[@SaiSatya]

The video could have been more elaborate by explaining the superposition of the two angular momenta.

[@balajee709]

NTA NEET test 36 -(q.26) A rod AB of length L and mass M is free to move on a frictionless horizontal surface.it is moving with a velocity v .end B of the rod AB strikes the end of the wall.assuming elastic impact,the angular velocity of the rod AB just after impact. Sir in this question,I understood how to do conservation of angular momentum about B but I couldn't understand how to write the equation for conservation of linear momentum .in solution it is given as this: mv = mwL/2 - mVcom Sir , how has this equation come. Also sir if possible please share with us your email id ,so can connect with you and send to you some good questions. Thanks you sir

[@yashpandey9550]

*city=Quite

[@chhavigupta2802]

whttt?

[@himanshuacharya215]

🙏 sita ram

[@beyondlogic112]

yahoo