Physics, the high-yield way

Mechanics & Rotational Motion High-yield

• Core kinematics equations for uniform acceleration: v = u + at, s = ut + ½at², v² = u² + 2as — know when each applies.
• Newton's three laws: inertia (1st), F = ma (2nd), action–reaction pairs (3rd); linear momentum (p = mv) is conserved in any closed system with no external force.
• Projectile motion splits into independent horizontal (constant velocity) and vertical (constant acceleration g) components; range R = u²sin2θ/g is maximum at θ = 45°.
• Work–energy theorem: net work done on an object equals its change in kinetic energy; mechanical energy (KE + PE) is conserved when only conservative forces act.
• Uniform circular motion requires a centripetal force directed toward the centre: Fc = mv²/r; this force does no work since it's always perpendicular to velocity.
• Torque τ = r × F (r Fsinθ) is the rotational analogue of force; net torque produces angular acceleration via τ = Iα, where I is the moment of inertia.
• Moment of inertia depends on mass distribution relative to the axis — a hollow cylinder has a larger I than a solid cylinder of the same mass and radius.
• Angular momentum (L = Iω) is conserved in the absence of external torque — the classic 'spinning skater pulls arms in and speeds up' scenario.
• Rolling without slipping combines translational KE (½mv²) and rotational KE (½Iω²) — a frequent calculation MCQ.

Electromagnetism & EM Induction High-yield

• Force on a moving charge in a magnetic field: F = qvB sinθ, direction given by the right-hand rule; force on a current-carrying conductor: F = BIL sinθ.
• A current-carrying wire generates a circular magnetic field around it (right-hand grip rule); a solenoid produces a uniform field inside, similar to a bar magnet.
• Faraday's law: induced EMF = −dΦ/dt, where Φ is magnetic flux (Φ = BA cosθ) — EMF is induced whenever flux through a circuit changes.
• Lenz's law states the induced current always flows in a direction that opposes the change producing it — a direct consequence of conservation of energy.
• Motional EMF is generated when a conductor moves through a magnetic field, cutting field lines (EMF = BLv for a rod moving perpendicular to B).
• Self-inductance opposes changes in current within the same coil; mutual inductance is the induction of EMF in one coil due to changing current in a neighbouring coil.
• Transformers use mutual induction between primary and secondary coils; turns ratio determines whether voltage is stepped up or down, with power (ideally) conserved (VpIp = VsIs).

Modern & Nuclear Physics High-yield

• Photoelectric effect: electrons are emitted only above a threshold frequency; Einstein's equation KEmax = hf − φ (φ = work function) explains why increasing intensity (not frequency) doesn't emit electrons below threshold.
• de Broglie proposed matter has wave-like properties: λ = h/p — the basis of wave–particle duality, later confirmed by electron diffraction.
• Bohr's model: electrons occupy fixed energy levels in the hydrogen atom; transitions between levels emit/absorb photons of specific energy, producing spectral line series (Lyman — UV, Balmer — visible, Paschen — IR).
• Atomic number (Z) = number of protons; mass number (A) = protons + neutrons; isotopes share Z but differ in neutron number (and so in A).
• Radioactive decay types: alpha (helium nucleus, low penetration, high ionising power), beta (electron, moderate penetration), gamma (high-energy photon, highest penetration, no charge/mass change).
• Radioactive decay follows N = N₀e^(−λt); half-life t½ = ln2/λ is the time for half the sample to decay, independent of the amount present.
• Nuclear fission splits a heavy nucleus into lighter ones (releases energy, basis of nuclear reactors/bombs); nuclear fusion combines light nuclei into a heavier one (powers the sun, releases even more energy per unit mass).
• Mass–energy equivalence (E = mc²) explains why the mass defect between reactants and products in nuclear reactions converts into released energy; the binding-energy-per-nucleon curve peaks around iron (Fe-56), explaining why fission of heavy elements and fusion of light elements both release energy.

Current Electricity High-yield

• Ohm's law: V = IR, valid for ohmic conductors at constant temperature; resistance R = ρL/A depends on resistivity, length, and cross-sectional area.
• Resistivity generally increases with temperature for metals (more lattice vibration/collisions) but decreases for semiconductors.
• Series circuits: same current through each resistor, resistances add directly (Rtotal = R1 + R2 + …); voltage divides.
• Parallel circuits: same voltage across each branch, reciprocal resistances add (1/Rtotal = 1/R1 + 1/R2 + …); current divides.
• Kirchhoff's current law: total current into a junction equals total current out (charge conservation); Kirchhoff's voltage law: the sum of EMFs and voltage drops around any closed loop is zero (energy conservation).
• Electrical power: P = VI = I²R = V²/R — know all three forms, as MCQs often give only two of the three variables (V, I, R).
• A real cell's terminal voltage is less than its EMF due to internal resistance: V = EMF − Ir.

Waves & Oscillations High-yield

• Simple harmonic motion (SHM): restoring force is proportional to displacement and directed opposite to it (F = −kx); displacement, velocity and acceleration are all sinusoidal functions of time.
• Time period formulas: spring–mass system T = 2π√(m/k); simple pendulum T = 2π√(L/g) — both are frequently used in calculation MCQs.
• Universal wave equation: v = fλ, relating wave speed, frequency and wavelength — applies to all wave types.
• Transverse waves oscillate perpendicular to the direction of travel (e.g. light, water surface waves); longitudinal waves oscillate parallel to the direction of travel (e.g. sound).
• Speed of sound depends on the medium (fastest in solids, slowest in gases) and increases with temperature in a given medium.
• The Doppler effect: apparent frequency increases as a source/observer approach each other and decreases as they move apart.
• Resonance occurs when a system is driven at its natural frequency, producing a dramatic increase in amplitude — the basis of standing wave formation in strings/air columns.
• Interference (constructive/destructive) and diffraction (bending around obstacles/through slits) are wave phenomena unique to waves, not particles — a common conceptual distinction tested alongside physical optics.