Physics Playground — Interactive Simulator
A hands-on physics sandbox you can actually play with. Launch a projectile and watch its arc, fling a planet into orbit, bounce balls and watch momentum and energy stay conserved, set a mass bouncing on a spring, or drag two wave sources to see an interference pattern ripple. Real equations run live in your browser — drag, aim, and tweak gravity, mass, and speed to see what happens.
How to Use
- Pick a simulation up top: **Projectile**, **Orbit**, **Collisions**, **Spring**, or **Waves**.
- For Projectile, drag on the canvas from the launch point to aim (angle + speed), or set the sliders, then press **Launch**. Try turning on air drag.
- For Orbit, drag out from any empty spot to fling a new body — the drag direction and length set its starting velocity. Change the central mass and gravity and watch the orbit change.
- For Collisions, click to drop a ball or drag to throw one; watch total momentum and kinetic energy in the readout (with bounce set to 100%, energy stays constant).
- For Spring, drag the mass and release it, then change the mass, stiffness, and damping. For Waves, drag the two sources and change the wavelength.
- Use **Play/Pause**, **Step**, **Reset**, and the **Speed** control any time. Everything runs locally — nothing is uploaded.
Controls
Readout
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How it works
The Physics Playground runs five classic simulations on a single canvas, each solving the real equations of motion every frame. Projectile integrates 2-D kinematics with an optional quadratic air-drag term and reports range, apex, flight time, and impact speed (it also draws the ideal drag-free arc for comparison). Orbit applies Newtonian gravity, a = GM/r², with velocity-style stepping so bodies trace stable circular, elliptical, or escape paths around a central mass — and can optionally attract each other. Collisions resolve as impulse exchanges that conserve momentum, with a restitution slider that makes them elastic (energy conserved) or inelastic (energy lost).
Spring solves the damped harmonic oscillator m·a = −k·x − c·v and plots position against time, with the natural period T = 2π√(m/k). Waves sums two point sources to show a live interference pattern of constructive and destructive bands. Everything is interactive — drag to aim or throw, move sources and masses, and change gravity, stiffness, or wavelength on the fly. It all runs in your browser; nothing is uploaded.
Reference
About the Physics Playground — Interactive Simulator
Working on science and engineering work? The Physics Playground — Interactive Simulator is a free browser tool that gives you the answer in seconds. A hands-on physics sandbox you can actually play with. Launch a projectile and watch its arc, fling a planet into orbit, bounce balls and watch momentum and energy stay conserved, set a mass bouncing on a spring, or drag two wave sources to see an interference pattern ripple. Real equations run live in your browser — drag, aim, and tweak gravity, mass, and speed to see what happens.
How it works
Type in what you have, and the answer shows up right away. Change anything and it updates by itself. Everything runs in your browser, so it is fast and nothing you type is sent away.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Is this a real physics engine or just an animation?
It's real physics. Each mode integrates the actual equations of motion every frame: projectiles use kinematics (with a quadratic air-drag option), orbits use Newtonian gravity with velocity-Verlet integration, collisions resolve with conservation-of-momentum impulses and a restitution setting, the spring solves the damped harmonic-oscillator equation, and the wave mode sums two sinusoidal sources. The numbers in the readout are computed, not faked.
How do I aim and launch the projectile?
Drag on the canvas starting from the launch point: the direction you drag sets the angle and the length sets the speed, just like pulling back a slingshot. Release to fire, or use the angle and speed sliders and press Launch. The tool reports range, maximum height, time of flight, and impact speed, and with drag off it also draws the ideal (no-air) path for comparison.
Why does kinetic energy drop in collisions sometimes?
That depends on the restitution (bounce) setting. At 100% the collisions are perfectly elastic, so total kinetic energy is conserved — you'll see it hold steady. Below 100% the collisions are inelastic: some kinetic energy is lost to the bounce each time (as it is in the real world), so the total falls. Momentum is conserved either way, which is exactly what the readout shows.
What does the Spring mode actually show?
It's a mass on a spring — a damped harmonic oscillator. You set the mass, the spring stiffness (k), and the damping, then displace the mass and let go. The animation shows the motion and a live position-vs-time graph, and the readout gives the natural period (T = 2π√(m/k)) and frequency. Crank up damping to watch the oscillation die away; set it to zero for endless bouncing.
Does any of this need the internet or send my data anywhere?
No. The whole simulator runs in your browser with plain JavaScript and a canvas — there are no servers, no accounts, and nothing you do is uploaded. You can use it offline once the page has loaded.
How do I use the Physics Playground — Interactive Simulator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
Learn or teach mechanics
See projectile arcs, orbits, momentum, and oscillation behave the way the equations say — a visual companion to a physics class.
Build intuition fast
Change one variable (gravity, mass, angle, stiffness) and watch the outcome change immediately, instead of re-doing the algebra.
Demonstrate conservation laws
Show momentum holding constant and energy conserved (or lost) in elastic vs inelastic collisions.
Explore orbits & gravity
Fling bodies at different speeds to get circular, elliptical, or escape trajectories around a central mass.
Just play
Bounce balls, sling planets, and ripple waves — a satisfying physics sandbox that happens to be accurate.
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