NCERT Solutions for Class 11 Physics Chapter 7 System of particles and Rotational Motion

NCERT Solutions for Class 11 Physics Chapter 7 System of particles and Rotational Motion

NCERT Solutions for Class 11 Physics Chapter 7 System of particles and Rotational Motion is designed and prepared by the best teachers across India. All the important topics are covered in the exercises and each answer comes with a detailed explanation to help students understand concepts better. These NCERT solutions play a crucial role in your preparation for all exams conducted by the CBSE, including the JEE.

NCERT TEXTBOOK QUESTIONS SOLVED

1. Give the location of the centre of mass of a (i) sphere, (ii) cylinder, (iii) ring, and (iv) cube, each of uniform mass density. Does the centre of mass of a body necessarily lie inside the body?

Ans. In all the four cases, as the mass density is uniform, centre of mass is located at their respective geometrical centres.
No, it is not necessary that the centre of mass of a body should lie on the body. For example, in case of a circular ring, centre of mass is at the centre of the ring, where there is no mass.

2. A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system?

Ans. When the child gets up and runs about on the trolley, the speed of the centre of mass of the trolley and child remains unchanged irrespective of the manner of motion of child. It is because here child and trolley constitute one single system and forces involved are purely internal forces. As there is no external force, there is no change in momentum of the system and velocity remains unchanged.

3. (a) Find the moment of inertia of a sphere about a tangent to the sphere, given the moment of inertia of the sphere about any of its diameters to be 2 MR2/5, where M is the mass of the sphere and R is the radius of the sphere.
(b) Given the moment of inertia of a disc of mass M and radius R about any of its diameters to 1 be 1/4 MR2, find the moment of inertia about an axis normal to the disc passing through a point on its edge.

Ans. (a) Moment of inertia of sphere about any diameter = 2/5 MR2
Applying theorem of parallel axes,Moment of inertia of sphere about a tangent to the sphere = 2/5 MR2 +M(R)2 =7/5 MR2
(b) We are given, moment of inertia of the disc about any of its diameters = 1/4 MR2
(i) Using theorem of perpendicular axes, moment of inertia of the disc about an axis passing through its centre and normal to the disc = 2 x 1/4 MR2 = 1/2 MR2.
(ii) Using theorem axes, moment of inertia of the disc passing through a point on its edge and normal to the dies = 1/2 MR2+ MR2 = 3/2 MR2.

4. Torques of equal magnitude are applied to a hollow cylinder and a solid sphere, both having the same mass and radius. The cylinder is free to rotate about its standard axis of symmetry, and the sphere is free to rotate about an axis passing through its centre. Which of the two will acquire a greater angular speed after a given time?

Ans. Let M be the mass and R the radius of the hollow cylinder, and also of the solid sphere. Their moments of inertia about the respective axes are I1 = MR2 and I2 = 2/5 MR2
Let τ be the magnitude of the torque applied to the cylinder and the sphere, producing angular accelerations α1and α2 respectively. Then τ=I1 α1 = I2 α2
The angular acceleration 04 produced in the sphere is larger. Hence, the sphere will acquire larger angular speed after a given time.

5. A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad s-1. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis?

Ans. M = 20 kg
Angular speed, w = 100 rad s-1; R = 0.25 m
Moment of inertia of the cylinder about its axis
=1/2 MR2 = 1/2 x 20 (0.25)2 kg m2 = 0.625 kg m2
Rotational kinetic energy,
Er = 1/2 Iw2 = 1/2 x 0.625 x (100)2 J = 3125 J
Angular momentum,
L = Iw = 0.625 x 100 Js= 62.5 Js.

Post your comments

Your mobile number will not be published.

View Comments

  • A.Nikhil Goud
  • 2024-February-10 02:44:01
Good wedsite nice
  • Raj
  • 2024-January-01 08:18:08
Good website
  • Mdiqbal Mdiqbal
  • 2023-September-01 03:08:35
Use full
  • Bandapalli siva ganga Devi
  • 2023-July-27 08:30:58
Super solutions
  • D BALAJI
  • 2023-May-22 03:18:23
Clear explanation
  • M venkata bramha chowdhary
  • 2023-May-16 12:21:53
Results
  • Dumpa snehith
  • 2023-May-01 05:12:48
Ncert to prepare for eamcet or eapcer
  • Gauri
  • 2023-January-05 08:05:07
Sabse khrab
  • Gauri
  • 2023-January-05 08:04:53
Sabse khrab
  • Prajoal
  • 2022-November-07 13:08:18
Verry good app
  • Preethi kumarK
  • 2022-April-04 08:42:37
I will very happy to sovle this mcqs
  • PradeepGupta
  • 2022-March-08 10:49:21
Super
  • Ashwani kumar
  • 2022-March-02 09:58:15
Nice
  • Ashwani kumar
  • 2022-March-02 09:58:04
Nice
  • Zyan safi
  • 2022-February-15 08:53:24
Nice
  • Zyan safi
  • 2022-February-15 08:53:12
Nice
  • Priyanshi
  • 2022-January-29 08:22:35
Thanks sir
  • Naria
  • 2022-January-24 09:11:38
Nice
  • ningu
  • 2022-January-08 08:56:50
good work sir
  • hs
  • 2021-December-06 08:44:35
good
  • prabhakar
  • 2021-November-05 13:29:34
How to download this
  • Dharmen
  • 2021-October-04 08:45:08
How to download
  • Anubhav
  • 2021-September-27 08:41:42
Math all chapter MCQ best
  • NIL
  • 2021-September-13 17:54:25
GOOD
  • Anjali
  • 2021-September-03 11:32:35
Ncert miscellaneous question pdf
  • Manjeet manjhi
  • 2021-September-02 08:25:59
Super
  • Karanveer Kaur
  • 2021-August-07 17:05:48
10 class workbook English answer
  • P.Ashrafbaig
  • 2021-August-06 17:34:20
My results How to check my 10th results
  • Asish Kumar sahu
  • 2021-July-30 15:35:38
Pls sir show my result my admit card is missing so I request you plz show my result
  • Varsha
  • 2021-July-29 14:58:13
This app is so..good it makes is understand better as we had seen many app with only answer we will not understand the method what they have done.....
  • Anupam
  • 2021-July-29 11:47:07
super
  • Lavanya vishawas Sonavale
  • 2021-July-28 08:23:33
Nice
  • Sudha
  • 2021-July-21 08:33:01
Super cute
  • Matruprasad nath
  • 2021-July-19 08:35:09
plese give me the answer for above question
  • Abhiram
  • 2021-July-17 10:49:18
8th class Telugu and maths social PDF text books
  • Abhiram
  • 2021-July-17 10:48:31
8th class Telugu and maths social PDF text books
  • Abhiram
  • 2021-July-17 10:48:21
8th class Telugu and maths social PDF text books
  • Aman
  • 2021-July-16 17:54:57
Nice
  • Patil yasvitah
  • 2021-July-15 08:48:58
S the practice question papers clasfrom foranothers districts of Karnataka 10th MCQ pattern 2021 exam 40 marks
  • Ajay
  • 2021-July-10 15:13:43
Basic questions
  • Nikki
  • 2021-July-03 16:36:13
How to download this pdf
  • Murali
  • 2021-June-29 17:38:23
How to get free download
  • Murali
  • 2021-June-29 17:38:23
How to get free download
  • Murali
  • 2021-June-29 17:38:13
How to get free download
  • Kurmapu rohini
  • 2021-June-26 17:51:15
How to download
  • Yashvanth
  • 2021-June-25 08:55:48
S PDF
  • Bhoomi
  • 2021-June-22 10:27:13
Nice this content is very helpful ....thnx a lot ..and pls expand the question there is only 58 which is less for class 10
  • Omkar
  • 2021-June-21 18:23:37
How to download
  • tanya shukla
  • 2021-June-14 09:27:07
hello thankyou so much it really helped me in my exam...........
  • Ranjith
  • 2021-June-11 09:43:25
Good
  • R sudha
  • 2021-June-05 18:16:47
Good
  • Urvi
  • 2021-April-08 13:34:59
Teacher
  • Rohit
  • 2021-April-06 08:36:53
Nice
  • HARSH RAJPUT DEVSARIYA 🙏🙏🙏🙏
  • 2021-March-04 14:03:46
Thanku for giving All chapter MCQ thanku you very much
  • Rakesh
  • 2021-February-18 08:58:15
I need 2019 10 Class Batch Results
  • Daripalli ramu
  • 2021-January-15 17:59:04
Super
  • Subash Gond
  • 2020-December-31 08:20:16
McQ question all chapter
  • Vandna
  • 2020-December-28 16:35:55
What,where and how lesson 1 class 6 pdf
  • Yuvraj yadav
  • 2020-December-19 09:45:44
Hi
  • Manasa
  • 2020-December-11 12:17:15
Good
  • Gundi.sonia
  • 2020-December-07 11:59:59
Hii
  • Dhanam jay
  • 2020-December-05 10:33:16
Very nice
  • Tanveer
  • 2020-December-02 14:50:15
Political Science question solution
  • Trilok
  • 2020-November-09 12:54:21
I like
  • Anshu poonia
  • 2020-October-24 15:03:52
Superb
  • Ranjan Baruah
  • 2020-October-22 09:02:59
Thank sir
  • MATHURAM
  • 2020-October-14 12:52:51
Need notes
  • Yadnyesh ubhad
  • 2020-October-12 08:42:03
So nice answer
  • Anusha chettri
  • 2020-October-09 13:21:16
Hello
  • Anusha chettri
  • 2020-October-09 13:20:28
Hello
  • Jasmita Naik
  • 2020-September-15 12:24:24
Thank you very much.... Sir we need more help from you.... From other subject also we need like this questions.. So please sir kindly help us through uploading questions from science... Please sir
  • Jasmita Naik
  • 2020-September-15 12:24:22
Thank you very much.... Sir we need more help from you.... From other subject also we need like this questions.. So please sir kindly help us through uploading questions from science... Please sir
  • Mohini
  • 2020-September-01 09:39:49
Kitne time se
  • Rajudutta
  • 2020-August-29 09:08:57
Excellent and reliable apps
  • SALMAN
  • 2020-August-28 09:54:17
I WANT 2019 ENGLISH CBSC CLASS 3RD COURSE BOOK SYLLABUS AND SOLUTIONS
  • ULRICA
  • 2020-August-20 18:23:29
It
  • Rishabh Kumar
  • 2020-August-20 12:06:16
Please give me
  • Chandra shekar
  • 2020-August-17 18:16:29
Mandasa
  • p.harshavardhan
  • 2020-August-17 09:41:40
Ok
  • Charchit
  • 2020-August-15 09:24:13
Yes they are all question are main
  • Muthalagu
  • 2020-August-10 13:04:53
10 A class
  • Vadde madhu
  • 2020-August-09 13:05:59
Hallo
  • Veeranna
  • 2020-August-04 18:04:29
1:1 2004
  • Eslavath Kalyan
  • 2020-July-29 13:13:11
Komatipalli kesamudram
  • Gumma pavan kalyan
  • 2020-July-27 19:15:47
Hall ticket
  • Rajudutta
  • 2020-July-21 14:09:35
Excellent solutions and easy to learn.
  • VAGEESHA
  • 2020-July-17 12:42:54
NICE JOB
  • Syed sayeed saaqib
  • 2020-July-17 09:17:31
10 th class marks
  • P.fairoz khan
  • 2020-July-17 09:17:26
My SSC result
  • Gangavarapu Ashok Reddy
  • 2020-July-16 18:48:26
10 the class 2020 markas
  • Kusi Mani kumaR
  • 2020-July-16 13:12:26
2008125010
  • suhailhajam
  • 2020-July-16 13:12:18
plz kindly MCQ question s
  • suhailhajam
  • 2020-July-16 09:23:15
plz kindly MCQ question s
  • Koripalli. Bindu ramya
  • 2020-July-16 09:23:07
Inter results second year
  • Faizan
  • 2020-July-15 19:05:41
Beautiful
  • K. Umesh Chandra
  • 2020-July-15 19:05:34
Please release 10th results
  • Surra naidu
  • 2020-July-15 18:11:06
S me result
  • Lakpathi
  • 2020-July-15 18:10:58
Cbse resuls
  • S.sravani
  • 2020-July-15 18:10:50
CBSE 10th class result
  • Gundrathi Mohan
  • 2020-July-15 18:10:35
S me results
  • Gundrathi Mohan
  • 2020-July-15 12:58:21
S me results
  • suhailhajam
  • 2020-July-15 12:02:02
plz kindly MCQ question s
  • chandar
  • 2020-July-15 12:01:55
chan
  • suhailhajam
  • 2020-July-15 09:56:17
plz kindly MCQ question s
  • Kaustab Roy
  • 2020-June-29 08:44:49
I want to explore everything
  • Anup
  • 2020-June-16 19:51:29
Workbook unit 1 exercise solution
  • Khushdeep Kaur
  • 2020-June-15 09:19:07
I want pdf of MCQ class 10th C.B.S.E
  • Saddam
  • 2020-June-09 15:24:13
Kindly s me 10 maths mcq question answer
  • SADDAM
  • 2020-June-08 14:24:07
SEND ME
  • Bed prakash
  • 2020-June-01 09:44:40
Mera result
  • palla sivaram
  • 2020-April-21 13:55:32
haiii
  • Dany
  • 2020-March-07 16:10:18
NCERT Solutions Very Good I Like It
  • laxman
  • 2020-February-17 15:31:16
good
  • Bhanusam.manjula
  • 2019-August-17 12:35:47
Ssc 2007batch regular halltichet number
  • Ramu
  • 2019-July-31 12:35:35
NCERT Solutions
  • Kalamata gowriswari
  • 2019-June-17 17:57:24
Open 10th result 2019ap
  • Nagra rayal
  • 2019-May-17 10:35:13
Yappudu 10th reselts
  • Yanati nagarani
  • 2019-May-17 10:20:31
10th result
  • NAGESWARA
  • 2019-May-11 18:30:50
How can see ssc ap 10th results
  • m.kalyani
  • 2019-May-11 18:30:36
10th result
  • Naveen
  • 2019-May-10 13:17:17
10th results
  • Sri kesav
  • 2019-May-10 09:58:50
Please tell me the correct date of AP ssc results
  • K. Sudhakar
  • 2019-May-10 09:58:43
Plz 10th result
  • V pawan durga sriniva
  • 2019-May-07 14:24:49
Please 10th cbsc results
  • V pawan durga sriniva
  • 2019-May-07 14:24:39
Please 10th cbsc results
  • Charan
  • 2019-May-07 14:24:21
Result ssc
  • Ayesha
  • 2019-May-07 14:24:17
At. What time did exam results will come?
  • Vadithya suresh
  • 2019-May-04 14:44:06
Results
  • VANKUDOTH pavan kalyan
  • 2018-May-30 10:16:07
Results
  • C H VAISHAVI
  • 2018-May-29 18:18:18
Cbse result by name
  • varunsai sanne
  • 2018-May-29 16:00:17
Xth results 2018
  • varunsai sanne
  • 2018-May-29 15:44:24
Xth results 2018
  • Yalagala Srihari
  • 2018-May-29 13:04:27
Exam results
  • Alpesh Dhamale
  • 2018-May-29 11:36:50
Nice article my baby wait for exam result i hope this year pass percentage may be increase
  • m. mohan rao
  • 2018-May-28 11:03:47
hi, s me cbse 10 class 2018 results
  • akshaya
  • 2018-May-26 10:22:07
at what time resilts are going to today
  • Velupala Ashwarya
  • 2018-May-15 11:01:52
My result
  • Ramu
  • 2018-May-12 16:09:34
good information