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Welcome to Class 11 Physics

A handful of laws explains how balls fly, satellites orbit, gases push and strings sing. This course builds them one idea at a time, with live labs, full solutions and Board, JEE and NEET practice.

1. What physics is for

Why does a cricket ball hit at $45^\circ$ go furthest? Why does a satellite not fall down — or rather, why does it keep falling without ever landing? Why does a pressure cooker cook faster, and why does a guitar string an octave higher have to be half as long? Questions like these look unrelated, yet they are all answered by a small number of laws: Newton's laws of motion, the law of gravitation, the conservation of energy and momentum, and the laws of thermodynamics. Physics is the search for such laws and the skill of using them to predict what will happen, with numbers.

Class 11 Physics is mostly mechanics — how things move and why — followed by the properties of solids and fluids, heat and thermodynamics, the kinetic theory of gases, and oscillations and waves. It is also the foundation for every engineering and medical entrance examination in India. The same physics serves the board exam, JEE Main, JEE Advanced and NEET; what changes is how deeply and how quickly you must use it.

📦 Class 10 gave you…

$$v=u+at$$ speed, force, work and power as formulas to substitute into.

🚀 Class 11 adds…

$$\mathbf{F}=m\mathbf{a}$$ vectors, rates of change, graphs, and the reasoning that produces the formulas.

2. How every section works

Each section is written for a student working alone. Read it in order, with a notebook and a calculator.

📘 Definitions and 📐 laws state each idea precisely, with all its conditions ("for constant acceleration only", "for small swings").
✏️ Worked examples come with step-by-step solutions hidden behind 💡 Show solution. Try each one first; then compare every step, not only the answer.
Two live interactives per section. Press ▶ Play, change the sliders, and predict what will happen before you look. They compute everything from the physics, so they are a laboratory you can always reach.
⚠️ Common mistakes boxes list the traps examiners set.
Exercises — 25 to 40 graded parts per section, each with a worked solution. Do them before opening the solutions.
🎯 Exam corner — original problems in the style of the Board paper, JEE Main, JEE Advanced and NEET, each tagged and fully solved, with an exam tip.
🔬 Research–Teaching Nexus — an optional half-hour investigation with real data, and a 🧪 five-question quiz to check yourself.

Underlined terms show a short definition when you point at them, and the Formula Sheet and Glossary collect everything in one place.

3. One throw, many chapters

Throw a ball. In the half-second it leaves your hand you have used half of this course. Its path is a projectile (Chapter 3) whose horizontal and vertical motions are independent straight-line motions (Chapter 2). Gravity is the only force (Chapters 4 and 7). As it climbs, kinetic energy turns into potential energy and back again (Chapter 5). If it spins, rotation enters (Chapter 6); if it is a football, air pressure and drag do (Chapter 9). Launch one yourself.

A $0.16\ \text{kg}$ ball is launched at speed $u$ and angle $\theta$ (no air resistance, $g=9.8\ \text{m/s}^2$). The path is drawn as it flies; the arrows show the horizontal and vertical parts of the velocity, and the bars show kinetic energy $K$, potential energy $U$ and their total. Notice which arrow never changes, and which bar never changes.

speed $u$ (m/s):20angle $\theta$:45°

time $t$ (s)—

range $R$ (m)—

maximum height $H$ (m)—

$K+U$ (J)—

✏️ Example 1 — A preview of Chapters 3 and 5

A $0.16\ \text{kg}$ ball is thrown at $20\ \text{m/s}$ at $45^\circ$ above the horizontal. Using results you will derive in Chapter 3 — range $R=\dfrac{u^2\sin2\theta}{g}$, maximum height $H=\dfrac{u^2\sin^2\theta}{2g}$ — find $R$ and $H$, and check that energy is conserved between the launch and the top of the path.

💡 Show solution▶

Range $R=\dfrac{(20)^2\sin90^\circ}{9.8}=\dfrac{400}{9.8}=40.8\ \text{m}$.

Height $H=\dfrac{(20)^2(0.7071)^2}{2(9.8)}=\dfrac{200}{19.6}=10.2\ \text{m}$.

Energy at launch $K=\tfrac12(0.16)(20)^2=32\ \text{J}$, $U=0$; total $32\ \text{J}$.

Energy at the top Only the horizontal velocity $u\cos45^\circ=14.1\ \text{m/s}$ remains, so $K=\tfrac12(0.16)(14.14)^2=16\ \text{J}$ and $U=mgH=(0.16)(9.8)(10.2)=16\ \text{J}$: total $32\ \text{J}$. ✓ Set $u=20$ and $\theta=45^\circ$ in the lab and compare.

4. The fourteen chapters at a glance

Measurement→Motion→Forces & energy→Rotation & gravity→Solids & fluids→Heat & gases→Oscillations & waves

Chapter 1

Units and Measurement

SI units, significant figures and dimensional analysis.

$[F]=[\text{M}\,\text{L}\,\text{T}^{-2}]$

Open chapter → Chapter 2

Motion in a Straight Line

Velocity as a rate, motion graphs, kinematic equations and free fall.

$x=ut+\tfrac12at^2$

Open chapter → Chapter 3

Motion in a Plane

Vectors, projectiles and uniform circular motion.

$R=\tfrac{u^2\sin2\theta}{g}$

Open chapter → Chapter 4

Laws of Motion

Newton's laws, momentum, friction and free-body diagrams.

$\mathbf{F}=\tfrac{d\mathbf{p}}{dt}$

Open chapter → Chapter 5

Work, Energy and Power

The work–energy theorem, conservation of energy, power and collisions.

$K=\tfrac12mv^2$

Open chapter → Chapter 6

System of Particles and Rotational Motion

Centre of mass, torque, angular momentum and moment of inertia.

$\tau=I\alpha$

Open chapter → Chapter 7

Gravitation

Kepler's laws, $g$ and its variation, escape speed and satellites.

$F=\tfrac{Gm_1m_2}{r^2}$

Open chapter → Chapter 8

Mechanical Properties of Solids

Stress, strain, Hooke's law and the elastic moduli.

$Y=\tfrac{\sigma}{\varepsilon}$

Open chapter → Chapter 9

Mechanical Properties of Fluids

Pressure, Bernoulli's principle, viscosity and surface tension.

$p+\tfrac12\rho v^2+\rho gh$

Open chapter → Chapter 10

Thermal Properties of Matter

Expansion, calorimetry, latent heat and heat transfer.

$Q=mc\,\Delta T$

Open chapter → Chapter 11

Thermodynamics

The first and second laws, processes and the Carnot engine.

$\Delta U=Q-W$

Open chapter → Chapter 12

Kinetic Theory

Pressure and temperature from molecules, equipartition and mean free path.

$p=\tfrac13\rho\overline{v^2}$

Open chapter → Chapter 13

Oscillations

Simple harmonic motion, energy, the spring and the pendulum.

$T=2\pi\sqrt{l/g}$

Open chapter → Chapter 14

Waves

Travelling waves, wave speed, superposition, standing waves and beats.

$y=a\sin(kx-\omega t)$

Open chapter →

5. Board, JEE and NEET: one course, four exams

The Board exam (CBSE or your State board) rewards clear explanations, derivations and neatly set-out numericals, often as 2-, 3- or 5-mark questions, case studies and assertion–reason items. JEE Main asks single-correct multiple-choice and numerical-value questions that need fluent problem solving under time pressure. JEE Advanced combines several ideas in one problem, with multi-correct, paragraph and matrix-match formats. NEET asks many quick single-correct questions that test concepts and fast, accurate arithmetic.

The teaching in every section follows the current Class 11 board syllabus. A few topics that were removed from the board syllabus are still examined in JEE or NEET — errors in measurement, relative velocity, the parallel- and perpendicular-axis theorems, rolling, and a few others. They appear only in clearly marked 🚀 Beyond the board syllabus boxes (each names the exams — JEE Main, NEET, JEE Advanced — that list its topic) and in Exam-corner problems tagged JEE or NEET, so a board-only student can skip them safely.

✅ Before you start

You need Class 10 Science (the physics chapters: motion, force, work and energy, light, electricity) and Class 10 mathematics — algebra, the laws of exponents, linear and quadratic equations, the trigonometric ratios $\sin$, $\cos$, $\tan$ of standard angles, coordinate geometry and reading graphs. Vectors and the small amount of calculus needed (rates of change, area under a graph) are taught inside this course when they are first used; Class 11 Mathematics, taken alongside, will prove the rules. Begin with Chapter 1 — Units and Measurement.

← Class 11 Physics — Contents Chapter 1 — Units and Measurement →