Balance Beam: The Principle of Moments
A metre rule on a movable pivot with a real torque engine: drag weights from the tray, stack them at any 5 cm notch, and watch the beam genuinely swing and settle — or tip onto its stops. A live moments ledger tallies every load's force × distance into clockwise and anticlockwise columns, the beam's own weight acts at its centre of gravity, and a mystery-mass challenge asks you to find a hidden mass using nothing but the principle of moments.
Drag weights from the tray onto the beam — stack them, or drag them off to remove. Drag the grey stand to move the pivot. Red arrow = the beam's own weight at its centre of gravity.
| Load | F (N) | d (m) | ACW (N·m) | CW (N·m) |
|---|---|---|---|---|
| beam (100 g) at 50 cm | 0.98 | 0.00 | ||
| Totals | 0.000 | 0.000 | ||
Unequal totals → a resultant moment → the beam turns towards the bigger side.
What Each Variable Means
Moment. The turning effect of a force about the pivot, in newton-metres (N·m).
Force. Here, the weight of each load: F = m·g, with g = 9.8 N/kg. Measured in newtons (N).
Perpendicular distance. From the pivot to the line of action of the force, in metres (m). The ledger lists d for every load.
Sum of. Add up every moment on that side of the pivot. When the two sums are equal, there is no resultant turning effect — the beam is in equilibrium.