What is centre of gravity?
Keep the heavy stuff low and in the middle and your model won't tip. Every model has a balance point called the centre of gravity. If it is above the wheels or feet, the model is stable. If it goes past the edge, it tips over! Heavy batteries belong low down.
Try Pendulum Metronome for freeComplete MightyCog booklet collection: 82 PDF booklets for $12.99. Instructions only; individual booklets remain free.
Explore the printable packTry it yourself
Tilt your model slowly. Where does it tip over?
Build it: 10 builds that teach centre of gravity
- ⏱️ Pendulum Metronome: Give it a nudge: tick… tock… tick. Move the wheel to another hole and count again! (level 1 of 5, about 10 minutes, 9 steps)
- ⚖️ Balance See-Saw: A see-saw that is also a scale. Can one gear beat two? (level 1 of 5, about 12 minutes, 10 steps)
- 🐦 Woodpecker Automaton: Turn the handle and the woodpecker pecks: tok-tok-tok-tok! (level 2 of 5, about 20 minutes, 16 steps)
- 🚧 Parking Barrier Gate: A long striped barrier that lifts with a tiny turn — thanks to a heavy counterweight. (level 2 of 5, about 20 minutes, 9 steps)
- 🌬️ Bevel-Gear Windmill: Turn the handwheel at the bottom — the sails spin at the top! (level 3 of 5, about 25 minutes, 16 steps)
- 🔋 Motor Buggy: Your first car that drives by itself — with a forwards/backwards switch and headlights! (level 3 of 5, about 30 minutes, 20 steps)
- 🎠 Chair-Swing Carousel: Crank faster and faster — the chairs fly out wider and wider! (level 2 of 5, about 35 minutes, 16 steps)
- 🐾 Twin-Spring 4×4: Two spring engines — one for the front wheels, one for the back. All four wheels push! (level 3 of 5, about 35 minutes, 16 steps)
- 🎡 Ferris Wheel: A big wheel turns slowly while its gondolas always hang the right way up. (level 3 of 5, about 45 minutes, 28 steps)
- 🛻 Bouncy Monster Truck: Four big wheels on four springy shock absorbers. Boing, boing! (level 4 of 5, about 45 minutes, 29 steps)
In the classroom
- E3 Strong & Steady (Explorers, Foundation)
- E6 Wind & Spin (Explorers, Foundation)
- I1 Forces & Motion (Inventors, Intermediate)
- I6 Bridges & Structures (Inventors, Intermediate)
- I10 Capstone: Fairground (Inventors, Intermediate)
Common engineering questions
How can I try centre of gravity at home?
Tilt your model slowly. Where does it tip over?
Which builds teach centre of gravity?
10 MightyCog builds teach it: Pendulum Metronome, Balance See-Saw, Woodpecker Automaton, Parking Barrier Gate and Bevel-Gear Windmill and more. Start with Pendulum Metronome: 9 steps, about 10 minutes.