What is the formula for Newton's Second Law?

Newton's Second Law of Motion is expressed as F_net = ma. It states that the net external force acting on an object is equal to the mass of the object multiplied by its acceleration. In terms of momentum, F = dp/dt.

What is the formula for Kinetic Energy?

The formula for Translational Kinetic Energy is K = (1/2)mv^2, where m is mass and v is velocity. In terms of momentum (p), it can be written as K = p^2 / 2m.

What is Coulomb's Law formula?

Coulomb's Law is given by F = k(q1*q2)/r^2, where F is the electrostatic force, q1 and q2 are the point charges, r is the distance between them, and k is Coulomb's constant (1 / 4πε0).

What is Einstein's Photoelectric Equation?

Einstein's Photoelectric Equation is K_max = hf - Φ, where K_max is the maximum kinetic energy of the emitted photoelectron, hf is the energy of the incident photon, and Φ is the work function of the material.

Physics Formulas &
Concept Explainers

A highly-structured, retrieval-optimized library designed for instant conceptual clarity. Stop memorizing symbols—understand the physics behind the equations.

Mechanics

Newton's Second Law of Motion

Definition

The rate of change of momentum of a body is directly proportional to the applied external net force, and takes place in the direction in which the force acts.

Fnet = m × a
(or F = dp/dt)

Variable Legend

Fnet = Net external force (Newtons, N)
m = Mass of the object (kg)
a = Acceleration vector (m/s²)

⚠️ Common Mistake (JEE/NEET)

Students often forget that F must be the net external force. Internal forces (like tension between two blocks moving together as a system) do not contribute to the acceleration of the center of mass of the entire system.

Translational Kinetic Energy

Definition

The energy possessed by a body by virtue of its linear motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

K = ½ m v2
(Momentum relation: K = p² / 2m)

Variable Legend

K = Kinetic Energy (Joules, J)
m = Mass (kg)
v = Velocity magnitude/speed (m/s)
p = Momentum (kg·m/s)

⚠️ Common Mistake (JEE/NEET)

Using velocity as a vector inside the square. Kinetic energy is a scalar quantity. It depends on the speed squared, not the velocity vector. Therefore, kinetic energy can never be negative.

Electrodynamics

Coulomb's Law

Definition

The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

F = k (|q1| |q2|) / r2

Variable Legend

F = Electrostatic Force (Newtons, N)
k = Coulomb's constant ≈ 9 × 109 N·m²/C²
q1, q2 = Point charges (Coulombs, C)
r = Distance between charges (m)

⚠️ Common Mistake (JEE/NEET)

Applying Coulomb's Law to extended charged bodies (like large spheres at close distances) instead of treating them purely as point charges or finding the correct effective center.

Modern Physics

Einstein's Photoelectric Equation

Definition

The maximum kinetic energy of an emitted photoelectron is equal to the energy of the incident photon minus the minimum energy required to eject the electron from the surface (work function).

Kmax = hf - Φ
(or eV0 = hc/λ - Φ)

Variable Legend

Kmax = Maximum Kinetic Energy (Joules or eV)
h = Planck's constant (6.626 × 10-34 J·s)
f = Frequency of incident light (Hz)
Φ (Phi) = Work function of the material (Joules or eV)
V0 = Stopping potential (Volts)

⚠️ Common Mistake (JEE/NEET)

Confusing the units. Work function and kinetic energy are frequently given in electron-volts (eV), but Planck's constant (h) is often used in SI units (J·s). Students forget to use the conversion 1 eV = 1.6 × 10-19 J, or use hc = 1240 eV·nm for faster calculations.

Memorizing formulas isn't enough.

If you struggle to know which formula to apply and when, you have a conceptual gap. Book a diagnostic session with Dr. Deepak Kumar to fix your physics reasoning framework.

Book a Diagnostic Session

Physics Formulas &Concept Explainers

Mechanics

Newton's Second Law of Motion

Translational Kinetic Energy

Electrodynamics

Coulomb's Law

Modern Physics

Einstein's Photoelectric Equation

Memorizing formulas isn't enough.

Physics Formulas &
Concept Explainers