Physics - Web Educationwebأ© ... This includes the JEE for the IITs and the AIEEE for the other engineering

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  • Physics MCQ

    Deb Mukherji, PhD

  • Preface

    The entrance examinations for almost all the premier engineering colleges of the country are presently in the multiple-choice format. This includes the JEE for the IITs and the AIEEE for the other engineering colleges of excellence. This book is designed as the basic study material in physics for these two tests and various other competitive examinations.

    Most of the problems presented in this book have actually evolved in my classrooms. While guiding students for competitive examinations for close to four decades, I have had to innovate problems to make them think. The sequence of their learning process has been first to grasp the basic concepts, then to correlate the problems with the concepts involved, and finally to get a lot of practice to achieve speed and accuracy. This book is a summary of my course material.

    I have found it very useful to summarize most of the concepts into single sentences. One may almost call them the sutras of +2 physics. Many of these one-liners appear in the solutions. The questions have been devised to drill the students in all possible applications of these concepts. To limit the size of the book, only those questions have been used which have proved most effective in my classrooms.

    This book is divided into nine parts. The first seven parts cover both theoretical and experimental physics, topicwise. One separate part is devoted to miscellaneous questions covering almost all types of objective questions that may be asked in the major competitive tests. Miscellaneous Questions—1 includes straight-objective questions of both single- and multiple-option-correct types. Miscellaneous Questions—2, 3 and 4 respectively contains assertion–reason-type, linked-comprehension-type and matrix-matching-type questions. The ninth part provides the students with several practice papers including model IIT-JEE test papers, which should help them take mock tests in a fixed time.

    Both the IIT-JEE and the AIEEE are based on questions that have only one correct choice. This book, however, has a large number of questions in which more than one answer may be correct. These are the teaching questions and train the students towards the comprehension which IIT-JEE demands. Moreover, these more-than-

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  • one-option-correct objective-type questions are sometimes asked in various tests other than IIT-JEE and AIEEE. Several test papers in the single-choice format should help in the final run-up.

    I hope that students and teachers will come forward with suggestions for improvements in the book. I thank the personnel in the editorial and production departments at Bharati Bhawan for their untiring efforts and enthusiasm in bringing out this book.

    Author

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  • To the Students

    The purpose of this book is twofold—first, to teach you the concepts required to tackle the IIT-JEE and AIEEE, and second, to provide practice material for these and other engineering entrance tests. Therefore, although it is possible to frame a large number of multiple-choice questions, in this book only those questions have been given which teach you important concepts and show you the different ways in which they can be applied. If you master these concepts, you can be reasonably sure of working out any multiple-choice question that comes your way.

    Some of the questions merit hints and some others, the full solutions. The hints and solutions are a very important part of the book. They will clarify your doubts and train you to think along the correct lines. Concepts and techniques which need special attention are highlighted with the TIP icon. Understand these well, for they have wide application.

    In most parts of the book, the straight-objective questions are divided into two types, approximately in equal numbers. Type 1 questions have only one correct option, whereas type 2 questions can have more than one correct option. In this book, there is no difference in the level of difficulty between the two types. However, type 2 questions are more demanding as every option has to be examined carefully. Try to reason out why each option is either correct or incorrect. This will teach you to think logically. They will also help you in comprehension-type questions. Look at the solutions to fine-tune your thinking.

    You will notice that some questions that have been asked in the previous IIT examinations have been included here. This is to give you an idea about the level of difficulty expected at the tests.

    The IIT entrance examinations of 2007 and 2008 have introduced three new question patterns, viz., linked-comprehension type, assertion–reason type and matrix-matring type. Assuming that future examinations would also include such questions, separate sections and chapters have been added to help you prepare for them.

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  • Contents

    Part 1. Mechanics 1-1–1-158

    1. Kinematics, Forces 1-3 Revision Exercise 1 1-49

    2. Circular, Rotational and Simple Harmonic Motions 1-63 3. Properties of Matter, Fluids 1-111

    Revision Exercise 2 1-146

    Part 2. Heat and Thermodynamics 2-1–2-40

    1. Heat and Thermodynamics 2-3

    Part 3. Sound 3-1–3-22

    1. Sound 3-3

    Part 4. Optics 4-1–4-28

    1. Optics 4-3

    Part 5. Electricity 5-1–5-176

    1. Electrostatics 5-3 Revision Exercise 3 5-45

    2. Electric Current in Conductors 5-56 3. Electromagnetism 5-97 4. Motion of Charged Particles 5-145

    Revision Exercise 4 5-164

    Part 6. Modern Physics 6-1–6-19

    1. Modern Physics 6-3

    Part 7. Experimental Physics 7-1–7-13

    1. Experimental Physics 7-3

    Part 8. Miscellaneous Questions 8-1–8-52

    1. Miscellaneous Questions—1 8-3 2. Miscellaneous Questions—2 8-31 3. Miscellaneous Questions—3 8-40 4. Miscellaneous Questions—4 8-47

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  • Part 9. Practice Test Papers 9-1–9-102

    Instructions 9-3

    1. Practice Worksheet—1 9-4 2. Practice Worksheet—2 9-19 3. Practice Worksheet—3 9-31 4. IIT Questions—1 9-44 5. IIT Questions—2 9-56 6. IIT Questions—3 9-69 7. IIT Questions—4 9-82 8. IIT Questions—5 9-95

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  • Part 1

    Mechanics

    1-1

  • 1

    Kinematics, Forces

     Type 1  Kinematics, Forces

    Choose the correct option (a, b, c or d).

    1. A particle has an initial velocity of 3î  4ĵ and an acceleration of 0.4î  0.3ĵ. Its speed after 10 s is

    (a) 10 units (b) 7 units

    (c) 72 units (d) 8.5 units

    2. A bird flies for 4 s with a velocity of |t  2| m/s in a straight line, where t  time in seconds. It covers a distance of

    (a) 2 m (b) 4 m (c) 6 m (d) 8 m

    3. A particle has an initial velocity of 9 m/s due east and a constant acceleration of 2 m/s2 due west. The distance covered by the particle in the fifth second of its motion is

    (a) 0 (b) 0.5 m (c) 2 m (d) none of these

    4. A particle moves in a straight line with a retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to

    (a) x (b) x2

    (c) ln x (d) ex

    1-3

  • 5. For a particle moving along a straight line, the displacement x depends on time t as x  t3  t2  t  . The ratio of its initial acceleration to its initial velocity depends

    (a) only on  and  (b) only on  and  (c) only on  and  (d) only on 

    6. From the top of a tower, a stone is thrown up and it reaches the ground in time t1. A second stone is thrown down with the same speed and it reaches the ground in time t2. A third stone is released from rest and it reaches the ground in time t3.

    (a) t3  1 2

    t1  t2 (b) t3  t1t2

    (c) 1 t3

     1 t2

     1 t1

    (d) t3 2  t1

    2  t2 2

    7. Water drops fall at regular intervals from a roof. At an instant when a drop is about to leave the roof, the separations between 3 successive drops below the roof are in the ratio

    (a) 1 : 2 : 3 (b) 1 : 4 : 9

    (c) 1 : 3 : 5 (d) 1 : 5 : 13

    8. Three particles A, B and C are thrown from the top of a tower with the same speed. A is thrown straight up, B is thrown straight down and C is thrown horizontally. They hit the ground with speeds vA, vB and vC respectively.

    (a) vA  vB  vC (b) vB  vC  vA (c) vA  vB  vC (d) vA  vB  vC

    9. A balloon starts rising from the ground with an acceleration of 1.25 m/s 2. After 8 s, a stone is released from the balloon. The stone will

    (a) cover a distance of 40 m

    (b) have a displacement of 50 m

    (c) reach the ground in 4 s

    (d) begin to move down after being released

    1-4 Physics MCQ

  • 10. A particle thrown up vertically reaches its highest point in time t1 and returns to the ground in a further time t2. The air resistance exerts a constant force on the particle opposite to its direction of motion.

    (a) t1  t2 (b) t1  t2 (c) t1  t2 (d) May be (a) or (c) depending on the ratio of the force of air

    resistance to the weight of the particle.

    11. An aeroplane flying at a constant velocity releases a bomb. As the bomb drops down from the aeroplane,

    (a) it will always be vertically below the aeroplane

    (b) it will always be vertically below the aeroplane only if the aeroplane is flying horizontally

    (c) it will always be vertically below the aeroplane only if the ae