Physics Formulas for JEE & NEET: High-Yield Revision Cheatsheet (Mechanics to Modern Physics)

Physics Formulas for JEE & NEET: High-Yield Revision Cheatsheet

Having formulas at your fingertips — along with the exact boundary conditions under which they apply — is the foundation of solving Physics problems rapidly in JEE Main, JEE Advanced, and NEET-UG.

1. Rotational Dynamics & Moment of Inertia

• Parallel Axis Theorem: $I = I_{ ext{cm}} + Md^2$ (Valid for any 3D rigid body).
• Perpendicular Axis Theorem: $I_z = I_x + I_y$ (Valid strictly for planar 2D laminar bodies lying in the $xy$-plane).
• Rolling Without Slipping: $v_{ ext{cm}} = omega R$ and $a_{ ext{cm}} = alpha R$.
• Acceleration on an Incline of Angle $heta$: a = rac{g sin heta}{1 + rac{I_{ ext{cm}}}{MR^2}}

2. Electrostatics & Capacitors

• Electric Field on Axial Line of Dipole: ec{E}_{ ext{axial}} = rac{1}{4piarepsilon_0} rac{2ec{p}}{r^3} (for $r gg a$).
• Electric Field on Equatorial Line: ec{E}_{ ext{eq}} = -rac{1}{4piarepsilon_0} rac{ec{p}}{r^3}.
• Energy Density of Electric Field: u_E = rac{1}{2}arepsilon_0 E^2.
• Common Potential When Sharing Charge: V_c = rac{C_1 V_1 + C_2 V_2}{C_1 + C_2}, and heat loss Delta H = rac{1}{2}rac{C_1 C_2}{C_1 + C_2}(V_1 - V_2)^2.

3. Magnetism & Electromagnetic Induction

• Biot-Savart Law: dec{B} = rac{mu_0}{4pi}rac{I (dec{l} imes ec{r})}{r^3}.
• Magnetic Field of Finite Straight Wire: B = rac{mu_0 I}{4pi d}(sin heta_1 + sin heta_2).
• Motional EMF: mathcal{E} = int (ec{v} imes ec{B}) cdot dec{l} (for straight rod perpendicular to ec{B} and ec{v}: $mathcal{E} = BvL$).

4. Modern Physics & Optics

• de Broglie Wavelength: lambda = rac{h}{p} = rac{h}{sqrt{2mK}} = rac{h}{sqrt{2mqV}}.
• Photoelectric Einstein Equation: K_{max} = eV_0 = rac{hc}{lambda} - phi_0.
• Lens Maker's Formula: rac{1}{f} = left(rac{mu_{ ext{lens}}}{mu_{ ext{medium}}} - 1 ight)left(rac{1}{R_1} - rac{1}{R_2} ight).