Center of Mass & Balance
Drag weights on a beam and place the support so it balances at the centre of mass.
Drag the coloured weights along the beam and drag the triangle support. The beam balances only when the support sits under the centre of mass.
About the Center of Mass & Balance
Free center of mass & balance. Drag weights on a beam and place the support so it balances at the centre of mass. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the center of mass & balance 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.
Drag weights on a beam and place the support so it balances at the centre of mass. 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 Center of Mass & Balance
- Use the controls to change Red weight, Blue weight, Green weight. The simulation reacts instantly.
- Press "Balance it for me", "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
- Balance the beam by moving only the support.
- Balance it by moving only a weight.
- Make one weight 10 kg and see how far the centre of mass moves.
Key ideas you can learn
- The centre of mass is the mass-weighted average position.
- A beam balances when the support is under the centre of mass.
- Torque = weight × distance from the pivot.
- Heavier weights pull the centre of mass towards them.
Where this is used in the real world
Cranes, ships, cars (low centre of mass for stability), gymnasts and high-jump athletes all use centre-of-mass thinking.
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
How do you find the centre of mass?
Sum of (mass × position) divided by total mass.
Why does a beam tip?
The torques on the two sides of the support are unequal.
Is the Center of Mass & Balance 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 Center of Mass & Balance 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.