Physics
132 concepts · 10 topics · K–12
Big questions physics answers
- What forces act on this object, and do they cancel?
- What energy did the system start with, and where did it go?
- How is the motion changing, and what is causing the change?
- Is this a wave, a particle, or both at once?
- Does this happen at everyday scales, or only at very fast or very small ones?
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How the topics connect
Every physics family on one map. Lines show shared prerequisites.
Explore by Topic
Motion & Change
Kinematics, velocity, acceleration, reference frames
14 conceptsForces & Interaction
Newton's laws, friction, gravity, momentum
29 conceptsEnergy & Systems
Work, power, conservation, thermodynamics
18 conceptsFluids & Thermodynamics
Density, pressure, buoyancy, heat, gases
7 conceptsWaves & Information
Sound, light, interference, signals
24 conceptsElectricity & Circuits
Charge, current, voltage, resistance, circuits
11 conceptsFields & Magnetism
Electric fields, magnetic fields, induction
12 conceptsGravitation & Orbits
Gravitational fields, satellites, escape velocity
3 conceptsOptics & Light
Visible light, mirrors, lenses, image formation
9 conceptsModern Physics
Radioactivity, quantum ideas, relativity
5 conceptsBrowse by Grade Band
Physics is usually taught by bands rather than single grades. Browse the concept library the same way.
Popular Concepts
Velocity
The rate of change of position with respect to time, including both magnitude and direction.
Acceleration
The rate at which an object's velocity changes over time, measured in metres per second squared (m/s²).
Force
A push or pull interaction between two objects that can cause a change in an object's velocity (speed or direction), described as a vector quantity.
Energy
The capacity to do work or cause change in a physical system, measured in joules (J).
Momentum
The product of an object's mass and velocity, representing the quantity of motion it carries.
Gravity
The universal attractive force between any two objects with mass, decreasing with the square of distance.
Friction
A contact force that opposes the relative motion or tendency of motion between two surfaces in contact.
Ohm's Law
The fundamental relationship stating that the voltage ($V$) across an ohmic conductor equals the current ($I$) flowing through it multiplied by its resistance ($R$).
Electric Current
Electric current is the rate at which electric charge flows past a point in a circuit or conductor.
Wave Speed
Wave speed is the distance a wave pattern travels each second through a medium.
Coulomb's Law
Coulomb's law gives the electric force between two point charges. The force gets larger when the charges are larger and gets smaller with the square.
Electromagnetic Induction
The process by which a changing magnetic flux through a conducting loop produces a voltage (electromotive force, EMF) across the conductor, which can drive a current around a closed circuit.
Work
The transfer of energy that occurs when a force causes an object to move through a distance in the direction of the force, calculated as $W = Fd\cos\theta$, where $\theta$ is the angle between the force and the displacement. Measured in joules (J).
Power
The rate at which work is done or energy is transferred, measured in watts (joules per second).
Physics Guides
In-depth guides and priority concept pages that go beyond short definitions with formulas, examples, common mistakes, and connected explanations.
Forces, Motion, and Energy
Speed, velocity, net force, mechanical energy, wave speed, and wavelength connected and explained.
Coulomb's Law
Definition, formula, examples, and common mistakes for electric force between charges.
Wave Speed
Clear definition, formula, examples, and the key idea that speed depends on the medium.
Electric Current
Rate of charge flow with formula, examples, and the circuit mistakes students make most often.
Features
Intuitive Explanations
Every concept is explained in plain language before the formulas, symbols, and details.
Connected Knowledge
Physics pages link strongly to related physics ideas so motion, forces, waves, and fields stay connected.
Interactive Playground
Visual simulations help you build intuition for motion, forces, energy, and wave behavior.
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