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

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.

Students can follow our channel updates on our facebook page.

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 -

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]

[yatharthdubey]

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.

[manaspatil]

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

[ranjitkalita]

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

[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❤️

[arshadmuhammed]

Sir you made me fall love with physics

[akshayanandtiwari]

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

[saivaraprasadkotha]

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

[sachinvarma]

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

[manishabhatnagar]

Sir please make a playlist of this series

[ujjwal]

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

[Dilip]

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.

[udaypatil]

Hello sir, I have one question to
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
By the way, you are 'Bestest Teacher' of PHYSICS I have ever

[sejalsangole]

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..🙏🏼

[sarthakverma]

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

[shubhammahajan]

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 help me out with this....

[kumardevada]

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?

[devjyotisahani]

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

[pranjalrathoreiitkharagpur]

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

[debabratapahari]

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 !!!!