Collision Lab: 2D Momentum & Kinetic Energy
Crash balls of different masses on a table and track total momentum and kinetic energy for bouncy or sticky collisions.
Drag a ball to move it. Drag the arrow tip to give it a velocity. Press Play and watch momentum and kinetic energy. Set the elasticity to 1 for bouncy balls or 0 for sticky ones. Walls push on the balls, so choose Wrap around to see momentum stay exactly the same.
About the Collision Lab: 2D Momentum & Kinetic Energy
Free collision lab: 2d momentum & kinetic energy. Crash balls of different masses on a table and track total momentum and kinetic energy for bouncy or sticky collisions. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the collision lab: 2d momentum & kinetic energy runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Crash balls of different masses on a table and track total momentum and kinetic energy for bouncy or sticky collisions. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Collision Lab: 2D Momentum & Kinetic Energy
- Use the controls to change Red ball mass, Blue ball mass, Green ball mass, Elasticity, Balls, and more. The simulation reacts instantly.
- Pick an option such as 2 balls, 3 balls, Bounce off walls, Wrap around to switch modes or load an example.
- Press "Pause", "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Set elasticity to 1 and watch the energy lost readout stay at zero.
- Set elasticity to 0 and see how much energy disappears.
- Give a light ball a big speed and hit a heavy ball.
- Turn on momentum arrows and check that they add up before and after a hit.
Key ideas you can learn
- Total momentum stays the same in every collision when no outside force acts.
- In a perfectly elastic collision kinetic energy is also conserved.
- In an inelastic collision some kinetic energy turns into heat and sound, but momentum is still conserved.
- The center of mass keeps moving at a constant velocity no matter how the balls collide.
Where this is used in the real world
Car safety design, billiards, particle physics and crash reconstruction all rely on conservation of momentum.
Who is this simulation for?
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is the difference between elastic and inelastic collisions?
Elastic collisions keep the total kinetic energy. Inelastic ones lose some. Momentum is conserved in both.
Why does the center of mass not change speed?
There is no net outside force on the group of balls, so their center of mass moves at a steady velocity.
Is the Collision Lab: 2D Momentum & Kinetic Energy free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Collision Lab: 2D Momentum & Kinetic Energy work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.