Newton’s Second Law (F = ma): The One Equation That Runs Everything If physics had a greatest hit, it’d be F = ma. Three letters, one equation, and it runs basically everything — from the arc of a thrown ball to the orbit of the Moon, from the crash testing of a car to the…
Energy is the most fundamental concept in physics — a conserved quantity that never changes in an isolated system. This guide covers kinetic energy, potential energy, conservation of energy, Noether’s theorem, E=mc², and every major energy form with clear explanations, formulas, and an interactive simulation.
Throw a ball, kick a football, fire a cannon — they all trace the same parabolic arc once they leave your hand. The secret to projectile motion is that horizontal and vertical are completely independent. Gravity pulls downward and doesn’t touch horizontal speed. A ball dropped from rest and a ball fired sideways from the same height hit the ground at exactly the same time. Master that independence, and every projectile problem becomes two simple one-dimensional problems stacked together.
A transverse wave doesn’t push forward — it shakes sideways. From light traveling across the universe to a guitar string vibrating under your fingers, transverse waves move energy perpendicular to their direction of travel. Understand them, and you unlock the physics behind everything you see and hear.
Momentum is always conserved — in every collision, explosion, and rocket launch. Learn what momentum is, how the law of conservation works, the difference between elastic and inelastic collisions, and why airbags save lives through the impulse-momentum theorem, all with clear examples and solved problems.
Every system — from engines to the human body — follows a simple rule: energy in equals energy out. This is the first law of thermodynamics, expressed as ΔU = Q − W, where changes in internal energy depend on heat added and work done. Though simple in principle, it explains everything from why engines need fuel to why perpetual motion machines are impossible, shaping how energy flows through the physical world.
Every object with mass pulls on every other object with mass — and one equation describes all of it. Newton’s law of universal gravitation, F = Gm₁m₂/r², governs everything from a falling apple to the orbit of the Moon. The force is always attractive, follows an inverse-square law, and scales with both masses. It took over a century after Newton to even measure the gravitational constant G, and scientists still only know it to about five significant figures.
There’s one equation at the heart of everything waves do — v = fλ. It connects wave speed, frequency, and wavelength in a relationship so clean it applies to every wave in the universe, from sound bouncing off walls to light crossing the vacuum of space. The medium sets the speed. The source sets the frequency. And the wavelength adjusts automatically to keep the equation balanced. Once you understand that, wave physics stops being confusing.
Newton’s three laws of motion are the foundation of classical mechanics — every push, pull, and collision follows them. From why objects resist change to how forces always come in pairs, these laws explain how everything moves and why. Clear explanations, real-world examples, and key formulas include
The air molecules around you right now are moving at about 500 meters per second — faster than most bullets. Yet you don’t feel a thing, because each molecule is unimaginably tiny and collides with its neighbours billions of times per second. Kinetic theory explains how this invisible chaos creates everything you can measure: pressure is just trillions of molecular impacts per second, temperature is just how fast the molecules are moving, and the ideal gas law PV = nRT falls straight out of Newton’s laws applied to bouncing particles.
End of content
End of content