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Every piece we've published, sorted by date. Each ends with worked problems and a FAQ.

Physics Fundamentals blog — long-form physics explainers, interactive labs and free calculators
What the blog covers, and where each topic starts.

What Is the Physics Fundamentals Blog?

The Physics Fundamentals blog is where each topic gets its long-form explanation: the idea first in plain language, then the mathematics, then worked examples — with an interactive lab and a calculator on the same page so you can test the result with your own numbers. Every article is fact-checked against standard references before it is published.

Where to start, by topic
TopicWhat it coversBrowse
ElectromagnetismThe physics of electric charge and magnetism, and of the fields that carry the force between them. It runs from the current in a wire to the light leaving a star, because visible light is itself an electromagnetic wave./blog/category/electromagnetism/
Fluid MechanicsThe physics of liquids and gases, at rest and in motion/blog/category/fluids/
KinematicsThe branch of mechanics that describes motion/blog/category/kinematics/
Classical MechanicsThe physics of why motion changes: the forces, energy and momentum that govern everything from a rolling ball to an orbiting satellite. Everything else in physics leans on it./blog/category/mechanics/
Modern PhysicsWhat happens when the classical picture breaks down/blog/category/modern-physics/
Nuclear PhysicsThe study of the nucleus: what holds it together, how it comes apart, and how much energy that releases. It is where a milligram of matter turns into the output of a power station./blog/category/nuclear-physics/
ThermodynamicsThe physics of heat, temperature and energy transfer in systems made of enormous numbers of particles/blog/category/thermodynamics/
Waves and OpticsOscillations that travel: sound and light, and what happens when a wave meets a boundary, a slit or a lens. The same mathematics describes a guitar string and a radio mast./blog/category/waves/
Ultraviolet Radiation: Types & Effects
Waves & Optics

Ultraviolet Radiation: Types & Effects

Ultraviolet radiation is the 100 to 400 nm region of the electromagnetic spectrum, split by convention into UVA, UVB and UVC. This page gives the three band boundaries and where they come from, the energy every ultraviolet photon carries in eV, joules and kJ/mol, which bands the atmosphere lets through and why, and the work-function threshold that explains why ultraviolet damages what visible light leaves alone. Seven worked problems, two original diagrams, an interactive lab and a calculator.

19 min read
Escape Velocity Explained: Formula, Five Worlds and Worked Examples
Classical Mechanics

Escape Velocity Explained: Formula, Five Worlds and Worked Examples

Escape velocity is the launch speed at which an unpowered object leaves a world for good: 11.18 km/s at Earth's surface, 2.375 km/s at the Moon's and 617.8 km/s at the Sun's. This page derives v = sqrt(2GM/r) from energy conservation, puts five worlds side by side against NASA's own published figures, shows why half the escape speed lifts a projectile only one third of a radius, and explains why no rocket ever has to reach 11.2 km/s. Seven worked problems, two original diagrams, an interactive lab and a calculator.

19 min read
Superconductors Explained: How Cold, How Much Field, How Much Current
Electromagnetism

Superconductors Explained: How Cold, How Much Field, How Much Current

A superconductor carries current with no measurable resistance below a critical temperature, and expels magnetic field while it does so. This page puts numbers on all three limits that end it: lead at 4.2 K holds 52.70 mT, a 1 mm-diameter lead wire carries 131.8 A for nothing where copper would burn 371.3 W per metre, and twenty-eight years of persistent current bound the resistance below 1.1 times ten to the minus eighteen ohms. Eight worked problems, three original diagrams, an interactive lab and a calculator.

22 min read
Eddy Currents: What They Are, What They Waste and Where They Help
Electromagnetism

Eddy Currents: What They Are, What They Waste and Where They Help

An eddy current is a loop of current a changing magnetic field drives inside solid metal, with no wire to guide it. In a thin sheet the power it wastes is P/V = pi^2 B^2 f^2 d^2 / (6 rho), which is why a metal core is cut into slices: the same 100 cubic centimetres of copper goes from 1300.08 W as one 20.0 mm block to 1.53 W as forty sheets. That is a cut of 849.79 times where the squared rule promises 1600, and this page measures exactly where the formula stops telling the truth. Eight worked problems, three original diagrams, an interactive lab and a calculator.

21 min read
Isothermal Process: What It Is and How to Find the Work
Thermodynamics

Isothermal Process: What It Is and How to Find the Work

An isothermal process holds the temperature still while the volume changes, so an ideal gas travels the curve PV = nRT and the work it does is the area underneath: W = nRT ln(V2/V1). One mole at 300 K doubling from 10.0 L to 20.0 L does 1728.8 J of work and draws in the same 1728.8 J as heat; let it expand freely into a vacuum between the same two states and it does none of it, while the entropy change stays at 5.763 J/K. Eight worked problems, three original diagrams, an interactive lab and a calculator.

23 min read
Jerk in Physics: What Happens When the Acceleration Itself Changes
Kinematics

Jerk in Physics: What Happens When the Acceleration Itself Changes

Jerk in physics is the rate at which an acceleration changes, and it is the quantity the familiar displacement formula has nowhere to put. Hold it constant and one more term appears, a sixth of the jerk times the time cubed, which is exactly what a constant-acceleration equation leaves out. Four of the five formulas a reader might reach for miss by exact amounts, including the one that looks most like a definition. Eight worked problems, three original diagrams, an interactive lab and a calculator.

21 min read
Radioactive Decay Chains: What Happens After the First Decay
Nuclear Physics

Radioactive Decay Chains: What Happens After the First Decay

A radioactive decay chain is what happens when the daughter of a decay is radioactive too: its activity climbs from zero, peaks at the exact instant it equals the parent's, and then falls in step with the parent that feeds it. Three regimes cover every case - secular, transient and no equilibrium at all - and which one you get depends only on the two half-lives. Eight worked problems on three real chains, three original diagrams, an interactive lab and a calculator.

18 min read
Thermal Diffusivity: How Fast Heat Really Moves Through a Material
Thermodynamics

Thermal Diffusivity: How Fast Heat Really Moves Through a Material

Thermal diffusivity is how fast a temperature change travels through a material, alpha = k divided by rho c, and it answers the question conductivity cannot: how long. A wall twice as thick takes four times as long to warm right through, still air outruns stainless steel, and a third quantity built from the same three properties decides why metal feels colder than wood. Eight worked problems, three original diagrams, an interactive lab and a calculator.

20 min read