Laws

Newton’s First Law

An object will remain at rest or move in a straight line at constant speed unless acted on by a resultant external force.

Newton’s Second Law

The acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass. Formula: F = ma

Newton’s Third Law

For every action, there is an equal and opposite reaction.

Law of Universal Gravitation

Every mass attracts every other mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Formula: F = G (m1 m2) / r²

Hooke’s Law

The force needed to extend or compress a spring is directly proportional to the extension or compression from its natural length. Formula: F = kx

Kepler’s First Law

Planets move in elliptical orbits with the Sun at one focus.

Kepler’s Second Law

A line that connects a planet to the Sun sweeps out equal areas in equal times.

Kepler’s Third Law

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. Formula: T² ∝ r³

Coulomb’s Law

The magnitude of the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. Formula: F = k (q1 q2) / r²

Ohm’s Law

The current through a conductor between two points is directly proportional to the voltage across the two points. Formula: V = IR

Kirchhoff’s First Law

The total current entering a junction equals the total current leaving the junction. Formula: ∑ I in = ∑ I out

Kirchhoff’s Second Law

The sum of the potential differences (voltage) in any closed loop in a circuit is equal to zero. Formula: ∑ V = 0

Principle of Superposition (for Waves)

When two or more waves overlap, the resultant displacement at any point is equal to the vector sum of the displacements of the individual waves at that point.

Snell’s Law (Law of Refraction)

The ratio of the sines of the angles of incidence and refraction is constant for a given pair of media. Formula: sin(i) / sin(r) = v1 / v2 = n

The First Law of Thermodynamics

The change in the internal energy of a system is equal to the heat added to the system minus the work done by the system. Formula: ΔU = Q - W

The Second Law of Thermodynamics

Heat cannot spontaneously flow from a colder body to a hotter body. The total entropy of an isolated system can never decrease over time.

Boyle’s Law

For a fixed mass of gas at constant temperature, the pressure of the gas is inversely proportional to its volume. Formula: P ∝ 1/V

Charles’s Law

For a fixed mass of gas at constant pressure, the volume of the gas is directly proportional to its absolute temperature. Formula: V ∝ T

Stefan-Boltzmann Law

The total energy radiated per unit surface area of a black body is directly proportional to the fourth power of the black body's temperature. Formula: P = σAT⁴

Wien’s Displacement Law

The wavelength at which the emission of a black body radiation is maximum is inversely proportional to the absolute temperature of the black body. Formula: λmax ∝ 1/T

Lenz’s Law

The direction of an induced current is such that it opposes the change in magnetic flux that caused it.

Faraday’s Law of Electromagnetic Induction

The induced electromotive force (EMF) in a closed loop is equal to the rate of change of magnetic flux through the loop. Formula: E = -dΦB/dt

Ampère’s Law

The magnetic field around a closed loop is proportional to the total current passing through the loop. Formula: ∮ B⋅dl = μ₀ I_enc

The Doppler Effect

The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. Formula (for sound): f' = f (v + vo)/(v - vs)

The Photoelectric Effect

The energy of a photon is proportional to its frequency. If the photon’s energy is greater than the work function, it can eject electrons from the surface. Formula: E = hf

De Broglie Hypothesis

Every particle has an associated wavelength, which is inversely proportional to its momentum. Formula: λ = h/p