Irodov Part 1 Mechanics — Which Problems to Solve for JEE

A section-by-section map of Part One of I.E. Irodov’s Problems in General Physics, checked against the JEE Main and JEE Advanced syllabuses.

Part One is the part of Irodov most students actually reach, and the part most worth reaching. Of its 388 problems, 289 sit in sections that are wholly on the JEE Advanced syllabus — the highest proportion anywhere in the book — and only one section is off it entirely.

What this part trains is not mechanics as such. You already know the mechanics. It trains the habit of writing the equations before writing any numbers: choosing the frame, naming the unknowns, deciding which conservation law applies and why, and carrying symbols all the way to the end. Irodov’s kinematics in particular is calculus-first, where most Indian problem sets are formula-first, and that difference is the real reason the section is worth the hours.

Key insight. Irodov’s mechanics is hard because the setup is hard, not because the algebra is. If you find yourself hunting for which formula applies, you are solving it the wrong way round — and the discomfort of that is precisely what the book is for.

The sections at a glance

Section 1.1 — Kinematics

Fifty-eight problems, all of them usable. The syllabus names kinematics in one and two dimensions, projectiles, uniform circular motion and relative velocity explicitly, and this section is built on exactly those.

It keeps returning to four things: integrating acceleration when it is a function of time, velocity or position rather than a constant; relative velocity as a vector subtraction rather than a rule; pursuit problems, where one body chases another and the direction of motion changes continuously; and constrained motion, where a string or rod ties two velocities together and the relation comes from differentiating a length.

Before you start it, be fluent with Motion in a Straight Line and Motion in a Plane. If graphical kinematics still needs thought, fix that first — Irodov assumes it.

Section 1.2 — The Fundamental Equation of Dynamics

Fifty-nine problems on Newton’s laws, friction, work and power, all in scope. The syllabus names “inertial and uniformly accelerated frames of reference”, so the pseudo-force problems set in a linearly accelerating frame — lifts, wedges, accelerating trolleys — are squarely on it rather than beyond it.

Two things here are not named: rotating frames, where a centrifugal term appears, and variable-mass systems such as rockets and falling chains. Both are standard Advanced preparation and do get asked, so they are worth doing; just know that you are past the printed syllabus when you do.

Before you start it: Laws of Motion.

Section 1.3 — Laws of Conservation of Energy, Momentum and Angular Momentum

The largest section in Part One at 82 problems, and the one with the best return. Energy, momentum and angular momentum conservation, collisions elastic and inelastic, centre-of-mass motion — all named on the syllabus, and Irodov’s treatment of when each law is available and when it is not is better than almost anything else in print.

Before you start it: Work, Energy and Power and Systems of Particles and Rotational Motion.

Section 1.4 — Universal Gravitation

Thirty-four problems, all in scope: gravitational field and potential, Kepler’s laws, escape velocity, orbits. Note that geostationary orbits are not on the JEE Main syllabus but are on the Advanced one, so the few problems touching them are worth doing only if Advanced is your target.

Before you start it: Gravitation.

Section 1.5 — Dynamics of a Solid Body

Fifty-six problems on moment of inertia, torque, angular momentum and rolling without slipping — all explicitly on the syllabus, both axis theorems included. The exception is the gyroscope: problems on precession are not on the syllabus and can be passed over.

Before you start it: Systems of Particles and Rotational Motion.

Section 1.6 — Elastic Deformations of a Solid Body

Twenty-five problems, of which roughly eleven are usable. The syllabus carries Hooke’s law and Young’s modulus, and separately “modulus of rigidity and bulk modulus in mechanics” — so all three moduli are on it. What it does not carry is what Irodov does with them: torsion of rods, bending of beams and strain energy in non-uniform bodies.

Solve stress-strain under a load, extension problems, and anything resting on the rigidity or bulk modulus directly. Skip the twisting couples and the bent beams.

Before you start it: Mechanical Properties of Solids.

Section 1.7 — Hydrodynamics

Twenty-five problems, of which perhaps fifteen are worth doing. This section is better value than its reputation: the syllabus carries Bernoulli’s theorem, continuity, Pascal’s law, buoyancy, viscosity, Stokes’ law and terminal velocity, which covers most of what Irodov asks here.

Solve the Bernoulli, continuity, efflux and terminal-velocity problems. Skip anything built on Poiseuille flow, Reynolds number or turbulence. The syllabus is unusually explicit here — it lists viscosity with “(Poiseuille’s equation excluded)” in brackets — and Reynolds number is not on the JEE Main syllabus at all.

Before you start it: Mechanical Properties of Fluids.

Section 1.8 — Relativistic Mechanics

Skip the entire section. Forty-nine problems, and relativity appears nowhere in the JEE Main or JEE Advanced syllabus. This is the single largest block of unusable problems in the book, and because it sits at the end of Part One, it is the first trap a student working in book order falls into.

Common mistakes with Part One

Solving it in order and stopping at 1.8. Forty-nine relativity problems is about a fortnight of evenings. Students frequently lose that fortnight, conclude Irodov is impossible, and abandon the book two sections before Electrodynamics, which carries as much in-scope work as the whole of Mechanics.

Starting at 1.1 with no calculus fluency. Irodov’s kinematics opens with acceleration as a function of velocity. If integrating $dv/dt = -kv$ is not routine, the physics will look harder than it is when the obstacle is the maths.

Treating 1.6 and 1.7 as full sections. They are short and mostly out of scope; between them they hold about 23 usable problems. Do not spend on them the time that 1.3 deserves.

Skipping 1.5 because rotation feels done. Rotation is the section where Advanced separates candidates most reliably, and Irodov’s rolling and angular-momentum problems are the best available practice for it.

What to read next

• Part 2 — Thermodynamics, the weakest part of the book for JEE
• Part 3 — Electrodynamics, which carries as much in-scope work as this one
• Should you solve Irodov at all? — the honest answer, with the hours it costs