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| Science NCERT Exemplar Solutions (Class 11th) | ||||||||||||||
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Class 11th Physics NCERT Exemplar Solutions
1. Introduction
This introductory chapter provides a broad overview of what physics is, exploring its vast scope, inherent excitement, and profound connection with technology and society. It emphasizes how physics seeks to explain the natural world through a limited number of fundamental laws. The chapter introduces the four fundamental forces in nature: the gravitational force, the electromagnetic force, the strong nuclear force, and the weak nuclear force. It also discusses the core philosophical pursuits in physics, such as unification (the attempt to explain diverse phenomena through a single theory) and reductionism (the attempt to understand complex systems by breaking them down into their constituent parts).
2. Units And Measurements
This chapter establishes the foundation of quantitative science by discussing the importance of measurement. It introduces the concepts of fundamental and derived physical quantities and details the International System of Units (SI). A central theme is dimensional analysis, a powerful technique used to check the consistency of physical equations and to derive relationships between physical quantities. The chapter thoroughly covers the concepts of accuracy and precision, different types of errors in measurement (systematic and random errors), and the rules for determining and calculating with significant figures. This provides the essential framework for recording and interpreting experimental data with scientific rigour.
3. Motion In A Straight Line
This chapter introduces kinematics, the study of motion, by focusing on the simplest case: rectilinear motion. It defines key concepts such as distance, displacement (a vector), speed, velocity (a vector), and acceleration. The chapter distinguishes between uniform and non-uniform motion and extensively uses graphical representations, like position-time and velocity-time graphs, to analyze motion visually. A major part of the chapter is dedicated to deriving and applying the three fundamental equations of uniformly accelerated motion: $v = u + at$, $s = ut + \frac{1}{2}at^2$, and $v^2 = u^2 + 2as$. These equations form the basis for solving a wide range of problems involving objects moving in a straight line.
4. Motion In A Plane
This chapter extends the study of kinematics to two dimensions, or motion in a plane. It begins by introducing the concept of vectors and scalars, and details the methods of vector addition, subtraction, and resolution. This vector analysis is then applied to describe two important types of motion. Projectile motion, the motion of an object thrown into the air under the influence of gravity, is analyzed by resolving its motion into independent horizontal and vertical components. Uniform circular motion is described as motion at a constant speed along a circular path, which involves a constantly changing velocity and hence a centripetal acceleration, $a_c = \frac{v^2}{r}$, directed towards the center of the circle.
5. Laws Of Motion
This chapter delves into dynamics, the study of the cause of motion, by presenting Newton's Three Laws of Motion. The First Law introduces the concept of inertia. The Second Law provides a quantitative definition of force as the rate of change of linear momentum ($\vec{F} = \frac{d\vec{p}}{dt}$), which simplifies to $\vec{F} = m\vec{a}$ for constant mass. The Third Law establishes the action-reaction principle. The chapter defines linear momentum ($\vec{p} = m\vec{v}$) and impulse. A crucial concept derived is the Law of Conservation of Linear Momentum, which is fundamental to understanding systems like collisions and explosions. It also discusses friction and the dynamics of circular motion.
6. Work, Energy And Power
This chapter introduces the interconnected concepts of work, energy, and power. Work is defined scientifically as the product of force and displacement in the direction of the force ($W = \vec{F} \cdot \vec{s}$). Energy is defined as the capacity to do work. The chapter focuses on mechanical energy, which includes Kinetic Energy (energy of motion, $K = \frac{1}{2}mv^2$) and Potential Energy (stored energy due to position, e.g., gravitational potential energy, $U = mgh$). The Work-Energy Theorem establishes a direct link between work done and the change in kinetic energy. The fundamental Law of Conservation of Energy is a central theme. Finally, Power is defined as the rate at which work is done ($P = \frac{dW}{dt}$).
7. System Of Particles And Rotational Motion
This chapter extends the principles of mechanics from point objects to extended rigid bodies, introducing rotational motion. It defines the center of mass of a system, a crucial concept for describing the motion of the system as a whole. The chapter then introduces rotational analogues to linear motion concepts: torque ($\vec{\tau} = \vec{r} \times \vec{F}$) is the rotational equivalent of force, angular momentum ($\vec{L} = \vec{r} \times \vec{p}$) corresponds to linear momentum, and moment of inertia ($I$) represents rotational inertia. Key principles like the conservation of angular momentum are discussed, which are essential for understanding the motion of spinning objects, from tops to planets.
8. Gravitation
This chapter explores the universal force of gravitation. It is centered around Newton's Law of Universal Gravitation, which states that the gravitational force between two masses is proportional to the product of the masses and inversely proportional to the square of the distance between them, $F = G\frac{m_1 m_2}{r^2}$. The chapter details the concept of acceleration due to gravity ($g$) and its variation with altitude and depth. It also covers gravitational potential energy, escape speed, and the orbital motion of satellites. The chapter connects these concepts to Kepler's laws of planetary motion, providing a comprehensive understanding of celestial mechanics.
9. Mechanical Properties Of Solids
This chapter investigates how solid materials respond to external forces, focusing on their elastic and plastic properties. It introduces the fundamental concepts of stress (internal restoring force per unit area) and strain (fractional change in dimension). The relationship between them is described by Hooke's Law, which states that within the elastic limit, stress is proportional to strain. This proportionality is quantified by various moduli of elasticity: Young’s Modulus ($Y$) for linear strain, the Shear Modulus ($G$) for shearing strain, and the Bulk Modulus ($B$) for volume strain. The stress-strain curve is used to characterize the behaviour of materials under load.
10. Mechanical Properties Of Fluids
This chapter covers the physics of fluids (liquids and gases). It is divided into fluid statics (fluids at rest) and fluid dynamics (fluids in motion). Statics includes concepts like pressure, density, Pascal's Law, and Archimedes' Principle, which explains buoyancy. Dynamics introduces concepts like streamline and turbulent flow, and the equation of continuity. A key principle is Bernoulli's principle ($P + \frac{1}{2}\rho v^2 + \rho gh = \text{constant}$), which is a statement of energy conservation for a flowing fluid. The chapter also discusses properties arising from intermolecular forces in fluids, such as viscosity (internal friction) and surface tension.
11. Thermal Properties Of Matter
This chapter deals with heat, temperature, and their effects on matter. It defines temperature and explains the different temperature scales. A major topic is thermal expansion of solids, liquids, and gases. The chapter introduces the concepts of specific heat capacity ($s$), which relates heat transfer to temperature change, and latent heat ($L$), the energy required for a change of phase (melting or boiling) at a constant temperature. It provides a detailed description of the three modes of heat transfer: conduction (through direct molecular collision), convection (through bulk movement of fluid), and radiation (through electromagnetic waves), including Newton's law of cooling.
12. Thermodynamics
This chapter lays down the fundamental laws governing heat and its transformation into other forms of energy. It introduces the Zeroth Law of Thermodynamics, which defines temperature. The First Law of Thermodynamics is a restatement of the law of conservation of energy for thermal systems ($\Delta U = Q - W$). The chapter describes various thermodynamic processes like isothermal, adiabatic, isobaric, and isochoric processes. The Second Law of Thermodynamics sets limits on the efficiency of converting heat into work and introduces the concept of entropy as a measure of disorder, dictating the direction of natural processes. It also explains the working principles of heat engines and refrigerators.
13. Kinetic Theory
This chapter provides a microscopic model to explain the macroscopic behaviour of gases, known as the Kinetic Theory of Gases. It is based on a set of assumptions about gas molecules being in continuous random motion. This theory successfully explains the gas laws and provides a molecular interpretation of pressure and temperature, showing that temperature is a measure of the average kinetic energy of the gas molecules. The chapter derives the expression for the pressure exerted by an ideal gas and deduces the ideal gas law. It introduces the concept of degrees of freedom and the Law of Equipartition of Energy to explain the specific heat capacities of gases.
14. Oscillations
This chapter focuses on oscillatory or periodic motion. It provides a detailed analysis of Simple Harmonic Motion (SHM), a special type of periodic motion where the restoring force is directly proportional to the displacement from the mean position ($F = -kx$). The chapter describes the kinematics of SHM, defining terms like amplitude, frequency, time period, and phase. It analyzes the energy transformations (kinetic and potential) in SHM, showing that the total mechanical energy is conserved. The chapter discusses examples of systems that exhibit SHM, such as a mass on a spring and a simple pendulum, and also introduces the concepts of damped and forced oscillations.
15. Waves
This chapter introduces the concept of wave motion as a means of transferring energy without transferring matter. It classifies waves into transverse and longitudinal types and describes the mathematical representation of a travelling wave. Key characteristics of a wave, such as wavelength ($\lambda$), frequency ($\nu$), and speed ($v = \nu\lambda$), are defined. The principle of superposition is a central theme, used to explain phenomena like interference (constructive and destructive), the formation of standing waves on a string and in pipes, and beats. The chapter also discusses the reflection of waves and introduces the Doppler effect, the apparent change in frequency due to relative motion between the source and observer.
Sample Paper I
This entry provides Sample Paper I, a comprehensive practice test for Class 11 Physics. It is carefully curated to reflect the syllabus and question patterns based on the NCERT Exemplar. The paper includes a diverse range of questions from all chapters, designed to test conceptual understanding, analytical reasoning, and problem-solving skills. By solving this paper, students can assess their level of preparation, practice time management, and gain valuable experience in tackling examination-style questions, making it an indispensable tool for effective revision.
Sample Paper II
This entry presents Sample Paper II, offering students another opportunity to test their knowledge and skills in Class 11 Physics. This paper provides a fresh set of questions covering the entire curriculum, from fundamental concepts to complex applications. Working through a second sample paper helps in reinforcing concepts, improving problem-solving speed and accuracy, and building confidence. It allows students to identify any remaining gaps in their understanding and to fine-tune their strategy for the final examination, ensuring a more thorough and robust preparation.