Balance Beam
Drag on the beam to move the weight, then lock in. Torque must match: mass times distance on each side.
How to play Balance Beam
A weight sits on the left side of a seesaw at a known distance from the pivot. You are given a second weight. Drag along the beam to slide it, watch the beam tilt, and press Lock in when you think it is level. You score a point when you are within 0.2 m of the exact spot. There are six rounds.
The physics behind it
A seesaw balances when the torques on both sides are equal. Torque is mass times distance from the pivot, so the rule is m₁ × d₁ = m₂ × d₂. With 6 kg at 4 m on the left and a 3 kg weight on the right, 3 × d₂ = 24, so d₂ = 8 m.
The same idea gives the center of mass of a group of objects: the mass-weighted average of their positions. The balance point is exactly where the beam would stay level if it rested on a single support.
Where this is used
Engineers use balance and center of mass to design vehicles, cranes and furniture that do not tip over. To try your own numbers, use the center of mass calculator for several masses and the moment of inertia calculator for how hard a shape is to spin.
Frequently asked questions
What makes a seesaw balance?
Equal torque on both sides: mass times distance from the pivot must match, so a lighter weight must sit farther out.
What is the center of mass?
The mass-weighted average position of an object or group of objects, where it would balance on one support.
How close do I need to get?
Within 0.2 m of the exact balance point for the round to count.
Is Balance Beam free?
Yes. It runs in your browser with no sign-up.
Related calculators
- Center of Mass Calculator: Center of mass calculator: find the balance point of up to three masses from their weights and x, y positions.
- Moment of Inertia Calculator: Moment of inertia calculator: find I for a cylinder, sphere, rod or point mass from its mass and radius or length.
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