Balancing Act: Torque & Seesaw
Balance a plank with bricks, crates and people, learn torque, and work out a mystery mass.
Drag the crates and people onto the plank. Balance it on the fulcrum by placing masses at the right distances (torque = mass × distance). Try the mystery mass challenge.
About the Balancing Act: Torque & Seesaw
Free balancing act: torque & seesaw. Balance a plank with bricks, crates and people, learn torque, and work out a mystery mass. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the balancing act: torque & seesaw 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.
Balance a plank with bricks, crates and people, learn torque, and work out a mystery 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 Balancing Act: Torque & Seesaw
- Use the controls to change Supports. The simulation reacts instantly.
- Pick an option such as Supports on, Supports off, Balance lab, Mystery mass to switch modes or load an example.
- Press "Reveal mystery", "Clear plank" 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 a 20 kg crate with a 10 kg brick.
- Put an adult and a kid on and balance them.
- Solve the mystery mass and press Reveal.
Key ideas you can learn
- Torque = force × distance from the pivot.
- A plank balances when the clockwise and anticlockwise torques are equal.
- A small mass far away can balance a big mass close in.
- You can find an unknown mass from balance.
Where this is used in the real world
Levers, cranes, scales, doors and even your own arm work on the principle of torque.
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 balance a seesaw?
Make the torque on the left (mass × distance) equal to the torque on the right.
How can you find a mystery mass?
Balance it with a known mass, then use m₁ d₁ = m₂ d₂ to solve for the unknown.
Is the Balancing Act: Torque & Seesaw 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 Balancing Act: Torque & Seesaw 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.