Block over Block Friction (Part-2) for JEE(Adv) | Class 11 Physics in Minutes|

In JEE Advanced topic of friction between block over block problems is very important and it forms the basic understanding in dynamics. Ashish Arora sir has explained all the concepts related to application of friction when a block over another block is placed and lower block is pulled by an external force. The concepts Analyzed in this video are given below.
Concept-1 : Block over block on smooth surface with external force on lower block
Concept-2 : Understanding and condition of common Motion of block with force on lower block
Concept-3 : Block over block on smooth surface with external force on upper block
Concept-4 : Limiting condition of common motion of blocks with force on upper block
Concept-5 : Block over block on rough surface with force on upper block
Concept-6 : Case analysis when upper limiting friction is smaller than lower limiting friction
Concept-7 : Case analysis when upper limiting friction is larger than lower limiting friction
Concept-8 : Understanding of case when lower block never slides
Concept-9 : Understanding of case when upper block never slides (when middle surface is smooth)
Concept-10 : Sliding condition in every case - friction at surface becomes equal to limiting friction
Detailed understanding of the concept can be covered through the Physics Galaxy Concept videos available through our channel playlist or our website.
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To understand all the applications of friction and dynamics, students can refer our Physics Galaxy series of books. These books are available for purchase at below link -
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Based on above video some questions are given below in comment section which students can solve and check if they are able to solve these questions using the concept explained in above video. Out of 5 questions given below for third question answers are not given. Students are advised to post the answer of this question in comments to discuss and verify if their answer is correct.
Practice Questions for students on concept of above video. Students are required to solve these questions and verify the answers given. Out of below given Solve the question, in ONE question given answer is wrong. Solve and post that question no of which answer is wrong and post the correct answer in comment section for discussion and verifying your result. In all below questions take g = 10m/s².
Practice Quiz Questions -
Q1. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontallay on 5kg block. Find at what value of F sliding will start between the two blocks ?
Ans [45N]
Q2. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontallay on 4kg block. Find at what value of F sliding will start between the two blocks ?
Ans [36N]
Q3. A 5kg block is placed over 10kg block on a smooth ground. Friction coefficient between 5kg and 10kg blocks is 0.2. A force F is applied horizontallay on 5kg block. Find at what value of F sliding will start between the two blocks ?
Ans [15N]
Q4. A 10kg block is placed over 20kg block on a rough ground. Friction coefficient between 20kg and ground is 0.2 and that between the two blocks is 0.1. A force F is applied horizontalay on 10kg block. Find at what value of F sliding will start between 20kg and ground then at which value sliding will start between the two blocks ?
Ans [On ground never start, between the blocks at 10N]
Q5. A 20kg block is placed over 20kg block on a rough ground. Friction coefficient between lower 20kg and ground is 0.1 and that between the two blocks is 0.6. A force F is applied horizontallay on upper 20kg block. Find at what value of F sliding will start between lower block and ground then at which value sliding will start between the two blocks ?
Ans [40N, 280N]
#physicsinminutes #physicsgalaxy #ashisharora #physicsgalaxypim

[@physicsgalaxyworld]

Practice Questions for students on concept of above video. Students are required to solve these questions and verify the answers given. Out of below given Solve the question, in ONE question given answer is wrong. Solve and post that question no of which answer is wrong and post the correct answer in comment section for discussion and verifying your result. In all below questions take g = 10m/s². Q1. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontallay on 5kg block. Find at what value of F sliding will start between the two blocks ? Ans [45N] Q2. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontallay on 4kg block. Find at what value of F sliding will start between the two blocks ? Ans [36N] Q3. A 5kg block is placed over 10kg block on a smooth ground. Friction coefficient between 5kg and 10kg blocks is 0.2. A force F is applied horizontallay on 5kg block. Find at what value of F sliding will start between the two blocks ? Ans [15N] Q4. A 10kg block is placed over 20kg block on a rough ground. Friction coefficient between 20kg and ground is 0.2 and that between the two blocks is 0.1. A force F is applied horizontalay on 10kg block. Find at what value of F sliding will start between 20kg and ground then at which value sliding will start between the two blocks ? Ans [On ground never start, between the blocks at 10N] Q5. A 20kg block is placed over 20kg block on a rough ground. Friction coefficient between lower 20kg and ground is 0.1 and that between the two blocks is 0.6. A force F is applied horizontallay on upper 20kg block. Find at what value of F sliding will start between lower block and ground then at which value sliding will start between the two blocks ? Ans [40N, 280N]

[@abhiramdharme3117]

All are correct

[@physicsgalaxyworld]

No one is incorrect !

[@bhaveshiitkanpur3329]

The answers for question no.5 are 40N and 200N

[@nandkishorkhaire7618]

Question 5 both answer are 200N

[@nandkishorkhaire7618]

And in 4th question I think the second part answer should be 15 N sir

[@yatharthdubey8358]

Correction ,F=200 N for sliding between blocks not 280 N,Thank you so much sir and you team for helping us in concept building.

[@manaspatil3996]

Just when you think a man cannot be any greater, Ashish Sir pushes the limit further. Need Work Energy next... Also 2021 Strategy...

[@vyankatiingle8819]

What are u doing now in 2024😊

[@ranjitkalita3734]

Sir you are a GOD 🧚🧚 for students from rural areas . Thank you sir🙏🙏🙏🙏

[@harshjha7685]

Very true..😊

[@shivendrasingh3318]

Why only for the students of rural area,????

[@spiritualindia5881]

Yaaaa

[@Uddaybhaikabaap]

Sir this physics in minutes series is awesome sir ❤️❤️ I owe you my greatest respect and admiration for the selfless service sir Thank you sir❤️

[@arshadmuhammed3261]

Sir you made me fall love with physics

[@sachinvarma8773]

Physics galaxy is a life saver... really a legendary channel. 🔥🔥 thnx team PG

[@physicsx8100]

Question no 5 Answer 40 , 200

[@physicsgalaxyworld]

Thats right ! Good going !

[@akshayanandtiwari]

When force reaches 40N downward sliding starts and when force is 200N there will be relative sliding between both blocks

[@manishabhatnagar6719]

Sir please make a playlist of this series

[@shinigami_1]

Done now..

[@Cric_sansu]

@@shinigami_1 what is name of this playlist

[@udaypatil1764]

Hello sir, I have one question to you..... Why you are not starting the Daily Live Courses for NEET & JEE aspirants? I asked you this question , bcoz I found that you are the only teacher who is teaching with better understanding without wasting time....... By the way, you are 'Bestest Teacher' of PHYSICS I have ever seen.................

[@raju6156]

Teacher ho toh ashish sir jesa!

[@11sfhunter47]

Q1. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontally on 5kg block. Find at what value of F sliding will start between the two blocks ? Ans [44.1N] Q2. A 4kg block is placed over 5kg block on a smooth ground. Friction coefficient between 5kg and 4kg is 0.5. A force F is applied horizontally on 4kg block. Find at what value of F sliding will start between the two blocks ? Ans [35.28N] Q3. A 5kg block is placed over 10kg block on a smooth ground. Friction coefficient between 5kg and 10kg blocks is 0.2. A force F is applied horizontally on 5kg block. Find at what value of F sliding will start between the two blocks ? Ans [14.7N] Q4. A 10kg block is placed over 20kg block on a rough ground. Friction coefficient between 20kg and ground is 0.2 and that between the two blocks is 0.1. A force F is applied horizontally on 10kg block. Find at what value of F sliding will start between 20kg and ground then at which value sliding will start between the two blocks ? Ans [sliding between block of 20kg and ground will never happen as F1L > F2L , 9.8N] Q5. A 20kg block is placed over 20kg block on a rough ground. Friction coefficient between lower 20kg and ground is 0.1 and that between the two blocks is 0.6. A force F is applied horizontally on upper 20kg block. Find at what value of F sliding will start between lower block and ground then at which value sliding will start between the two blocks ? Ans [39.2N, 196N] Last questions answer is 196N not 280N

[@pushkarrai9033]

its been 2 years since your reply but did you take g=9.8 m/s^2 ?

[@abhimanyupareek1618]

sir your method of teaching us is fabulous and u are the best teacher in the world love you sir...........

[@sejalsangole2527]

In 5th question the answer is wrong.. Correct answer should be 40N and 200N... according to me.. Am I correct?? And Sir thank you so much.. Physics Galaxy has helped me a lot in Physics..🙏🏼

[@physicsgalaxyworld]

Thats right ! Good going !

[@saathviksutarsaathvik_IIT25]

@@physicsgalaxyworld shouldn't F=120N in the last question as 240-120 because f2L=120N???

[@omraanedits6374]

Make a playlist of this series...

[@ahmadshaikh7494]

Sir now I understood clearly thanks ,and I was able to do all questions.

[@abhinavsharma2442]

Pls continue these series not only for mechanics but also for others topics also its a request

[@basudevbehera1290]

Lat question i.e fifth question force required to get sliding between blocks is 200N

[@romikumarsingh1514]

Physics galaxy is really galaxy for physics

[@abhiruprudra1889]

5. 40N, 200N

[@jeestar3054]

A lot of thanks sir..u are great 🙏🙏🙏🙏🙏

[@Ykr1030]

All are correct 💯

[@PhysicsbyPuneetSir]

We love u Ashish sir...

[@shahajimadale3262]

Sir ur checklist videos helped me alot. In jan 1st attempt. I was not aware of ur channel. At that time I solved only 9 ques. I came to know about ur channel in April. I watched all checklist videos in lockdown. In Sept jee main i attemped 18 ques of physics. Remaining 7 also could be done. As u mentioned in checklist videos but I couldn't found trigger point at that time. But sir thanks a alot. 🙏🙏🙏

[@physicsgalaxyworld]

Great Suyash! All the best for the upcoming competitions.

[@shahajimadale3262]

@GLOBAL POT 😅😅😅🤣🤣🤣 Hai bhai 16 toh pakka correct hai. 2 me zara idhar udhar hua.

[@pankajkumarpradhan6333]

SIR I'M FOLLOWING YOUR PHYSICS GALAXY BOOKS BUT IT DOESN'T INCLUDE SEMICONDUCTORS SO SIR PLZ TRY TO INCLUDE THIS TOPIC IN OPTICS AND MODERN PHYSICS BOOK ... IN NEXT EDITION

[@gauravsrule451]

Q5) ans is 200N

[@romikumarsingh1514]

Sr very thankful for helping us 🙏

[@GabbarSingh-td1mb]

I learn the block over block problem from physics galaxy.. Thanku sir and physics galaxy .

[@harshitbhalla9274]

Sir I think 5th answer is 40/200 and thats why its incorrect. Thank you very much sir for all these concept videos on physics. They are the best in full youtube.

[@shawol275]

Thank you so much sir . You have cleared every concept.

[@namratabhatta6015]

Thankyou for such an excellent explanation.

[@shivganeshfoujdar4385]

please stop making poji work .its child labour. let him study

[@khushi37272]

😂😂

[@----TheMostG]

Underrated comment😂😂

[@debarghya_das]

😂😂😂

[@saivaraprasadkotha1333]

Sir, 5th question answer is 40N,200N Please tell whether I am correct?

[@shivamverma9447]

Thanks sir❤️😇

[@diddesekhar768]

Sir very fantastic explanation that reaches eceryone

[@gaurav510]

Ans 5 is 40N and 200 N

[@chandrakantpatil4203]

Sir kuch jee 2021 ke liye bhi... I love your concepts.. Thank you sir

[@physicsgalaxyworld]

ye hain beta for jee 2021 too Also, aap concept videos refer kar sakte hain kzbin.infoplaylists?view=50&sort=dd&shelf_id=5

[@bhanuchoudhary8796]

Thanks sir 👍

[@harshjha7685]

Q.5 at 200N sliding will start btw the blocks..

[@a2zfreaker729]

those who have disliked has kept their mobile in opposite direction such that it seems to them like

[@ujjwal4896]

Should I practice advance illustrations playlist for KVPY SX ???? And which book I should practice for KVPY based questions. ???

[@physicsgalaxyworld]

For KVPY you should focus on PYQs and conceptual MCQs of PG books

[@kunalrajput4421]

Q) = 40N and 200N

[@jaynagwani4309]

Dhanywaad sir ji

[@_UjjawalSinha_]

Nice explaination Sir👌

[@devjyotisahani7896]

Sir Answer of 5 th question is wrong . According to me Correct answer will be 40 N and 200N.

[@Narendrakumar-bt9ss]

Sir, oscillation rotation magnetism question for neet, plzzzzz sir...only few days left

[@sagnikmajumder1650]

In 5th problem...answer of the second case is 200N

[@movie_shorts_07]

Question 5 ( 40 ; 200 )

[@Dilip077]

Sir, as far as I know magnet is a type of iron oxide.Then how can it create magnetic field around it? Whereas metals cannot create a magnetic field around it for having same number of positive and negative charges . Apologizing for my bad English. I am from a small village school(Bengali medium).So, I don't know much English.

[@shubhammahajan3745]

Well i don't know ur question's answer but definitely u know English better than those studying in English medium...and let me tell u there is no grammatical mistake in ur comment

[@nishugupta7729]

In question 5 it should be [40, 200]

[@priyagupta9118]

Beautifully explained

[@anjanagupta4289]

sir how to get mentorship fromu love u pls tell

[@naitejas5761]

Sir , plz make video of ray optics

[@Pranil521]

sir according to me the answer of second part of fifth question should be 200N. And sir by the way your teaching is awesome..

[@shahajimadale3262]

Sir 3 block system me problem ati hai. Pls guide sir. 🙏🙏

[@physicsgalaxyworld]

Don't worry about 3 blocks, not required for JEE advanced.

[@physicsgalaxyworld]

Still, in upcoming PIM videos sir will cover these

[@shahajimadale3262]

@@physicsgalaxyworld ok sir thanks

[@indianhindistories944]

Nice sir thank u

[@rekhajain1978]

How to solve q5 part 1....plz help

[@prakharjain1228]

Chalo ab jakar samaz aaya..

[@rishabmishra6957]

Thank you so much sir ❤️

[@Abhijeet_17.]

Sir is this series gonna be chapter wise or topic importance wise . Please reply

[@kumardevada8567]

Sir, when upper block starts sliding on lower block, what happens to the motion of lower block, will it moves or not, if it moves, what is the acceleration of lower block?

[@shivendrasingh3318]

Sir at 2:43,how will both the blocks start moving together. The forces on upper block are the friction and F, and it will start moving only when F will be bigger than limiting value of friction, than how can both the blocks move together as soon as the force F is applied. Please clear this doubt as soon as possible sir. Thank you.

[@गणितशिक्षा]

See at any F , f2 willl act forward on m1 and grou d is smooth which imply m1 will definitely move and since m2 is kept over m1 which imply as m1 moves m2 also moves which imply for any F, system will move !!!!!!😀😀

[@shubhammahajan3745]

@@गणितशिक्षा the question isn't that whether they move or nor but is why do they move together

[@shubhammahajan3745]

@@गणितशिक्षा the question isn't that whether they move or nor but is why do they move together

[@shobhitsingh4434]

God level explainer

[@sarthakverma1513]

Sir checklist videos abhi iss year 2021 aspirants ke liye bhi available rahengi ya phir delete ho jayengi thodi din mein.please clear????

[@aishwary959]

Sir pls upload these videos fast so that we can revise concept before jee advance 2020

[@debabratapahari1263]

Hello Sir !!! Myself Pratyush Pahari. Sir, I have done many mistakes in class 11 and 12. So, I want to take drop for Neet 2021. If I watched all Concept Videos of Physics Galaxy, Can I score 150+ in Neet 2021 ?? Also tell me what should I do additionally ?? Sir, I urgly request you to kindly reply me. Take my heartiest respect and pranam !!!!

[@DeepakKumar-fi4os]

How much you scored ?

[@priyanshjain140]

Sir what if more than 2 blocks are there??.

[@physicsgalaxyworld]

It will come up soon...

[@priyanshjain140]

@@physicsgalaxyworld Sir plz also see the COM frame of reference concept!!!

[@shobhitsingh4434]

Huge respect sir

[@reviewer3771]

In the last question for sliding bw blocks F = 200 N not 280.

[@geethusharma1857]

for last question force for sliding is 200

[@krishankant5289]

wrong answer is 5th ka second part😀 Thank you sir ji😊🙏

[@pranjalrathoreiitkharagpur2201]

(()()(){DOUBT}()()() ..........................SIR IN FIRST EXAMPLE WHY DID WE HAVE NOT TAKEN .....COMMON ACCELERATION AS =(F-f2)/(m1+m2).... as you have told friction f2 will be acting on the block of mass m1....... ??? plese explain it

[@Lightyearfar]

Lower surface is smooth bro,and friction is internal force in that case

[@shubhammahajan3745]

For two block system will both either have common acceleration or one will have some acceleration and other will be at rest???? R there any other cases???? I am so confused about the acceleration......plz help me out with this....

[@healthexpert427]

Ques 3 ) Ans is 30 N and Ques 5) Second ans is 200 N...please tell me whether my answer is right or wrong?

[@physicsgalaxyworld]

Your Q5 ans is correct

[@chandanbharti5207]

Thank sir

[@diddesekhar768]

Sir please explain more than 2 blocks and force applied on two or three blocks in opposite directions

[@adityagautam3072]

thank you sir

[@jayshreepatil7805]

Sir why you are not taking live cources for jee and neet throughout the year?.......

[@leomessi-bm6if]

Sir..I think that the answer for the 5th q will be 40N and 200N

[@sarika7069]

5 th questions ans. Is wrong . Correct ans. Is 40 N and 240 N respectively.

[@kanswaskapoor165]

Sir please continue the series.🙏

[@kingm2759]

SIR... SIRF 4 DIN BAAKI HE NEET KE liye.... Plz app kuch ese 10 min concept videos banado neet point of view se.... Plz sir... Plz sir.... Bas kuch videos banado ...ek baar important concepts revise ho jaega.... Plz sir.... 🙏🙏🙏🙏🙏🙏

[@krishnavchoudhury5303]

Sir please make a video on projectile motion on an inclined plane ...

[@aryansingharyansingh5750]

Sir what we should refer for class 11 kvpy

[@ganeshramakrishnan3533]

In 5th question ,it should be 40N, 200N

[@srividyaganesh5830]

The answer of 5th question would be 40 N, 200 N

[@amanvishwakarma7792]

The answer to last question is 40 and 200N

[@jade-zc2bz]

all are correct

[@pankajkumarpradhan6333]

SIR I CAN'T FIND THE PLAYLISTS OF HYBRID PHYSICS AND PG FUNDAMENTAL CLASSES ..... SO SIR PLZ HELP ME.....

[@physicsgalaxyworld]

PG Concept videos for class XI: kzbin.infoplaylists?view=50&sort=dd&shelf_id=1 for Class XII: kzbin.infoplaylists?view=50&sort=dd&shelf_id=5

[@pankajkumarpradhan6333]

@@physicsgalaxyworld SIR BUT THESE ARE CONCEPT VIDEOS BUT I NEED THE LINK FOR LIVE STREAM VIDEOS WHICH YOU HAVE NAMED AS PG FUNDAMENTAL CLASSES AND THOSE WHICH ARE HYBRID PHYSICS LECTURES... SO SIR PLZ TELL

[@akashsamanta421]

BHAI TU TYPE KAR , *PHYSICS GALAXY REVISION CHECKLIST* 1ST VIDEO AAYEGA JISME 55 KE AAS PASS VIDEO KI CHECKLIST HOGI , 🤷‍♂️🤷‍♂️🤷‍♂️🤷‍♂️

[@thiscommetwastyped8695]

kzbin.info/aero/PLEmavoh9cLs2gLWHuLl1wLz31r9sHv3vX

[@pankajkumarpradhan6333]

@@akashsamanta421 bhai tu odisha se hai na ??

[@Jin.oppas_left_hand]

Is there any playlist of this???

[@meet-thetechtips1252]

Sir ,please keep one class for advanced level RC,LC ckts also

[@physicsgalaxyworld]

coming up

[@meet-thetechtips1252]

@@physicsgalaxyworld Thankyou sir ! My jee mains went very well now gearing up for advanced with your blessings!

[@priyanshgupta7459]

Sir is it always true that the force required to move the whole system is always less than the force to slide the 2 blocks??

[@rishabmishra6957]

yes, always

[@narsimhanayak6652]

Tq sir for a wonderful session really I have cleared all the questions in the comment section . Thank you

[@moderngamer2124]

Accha hai sir

[@neet-tt1bj]

CORRECTION :- QUES 5 PAAR SIR JO FORCE F ,,, DONO BLOCKS KO SLIDE KAREGA USKA VALUE 200 N ATAH HEIN 280 NEHI

[@mannekumaraswamy]

sir please do video on 3 blocks system

[@lsuneeta7535]

Sir can u make video on errors and measurements please

[@steyn4922]

sir can u take an example where the top block is connected to a spring

[@adityaroy-zg8xw]

Just F ki jgh speing force aayega

[@anishaagarwal7265]

Sir i am not getting answer of Q5 as 40 and 200 My f1 for lower block is coming as 20 and F is 220 Where i am wrong plz tell