Place a 2kg mass at 1m left. Where must a 4kg mass go to balance?

You can work it out this way: use τ = mgd: 2×1 = 4×d.

Can two equal masses at equal distances ever be unbalanced?

You can work it out this way: think about what torque = r × F means when r and F are equal.

Pro 🔒~15 min

Balancing Act

Discover torque and rotational equilibrium

How it works

Balancing Act demonstrates a key principle: An object is in rotational equilibrium when the net torque about any pivot point is zero. An object is in rotational equilibrium when the net torque about any pivot point is zero. Torque is the product of force and the perpendicular distance from the pivot (lever arm). The law of moments states that clockwise torques must equal counterclockwise torques for balance. This principle underlies levers, seesaws, and structural engineering.

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Step-by-step

Drag masses onto the balance beam.
The beam tilts when torques are unequal.
Balance by adjusting mass values or positions.
Use the ruler to measure lever arm distances.

Key formulas

$\tau = r \times F$ Torque
$\sum \tau = 0$ Rotational equilibrium condition
$\tau = m \cdot g \cdot d$ Torque from weight

Frequently asked questions

Place a 2kg mass at 1m left. Where must a 4kg mass go to balance?: You can work it out this way: use τ = mgd: 2×1 = 4×d.
Can two equal masses at equal distances ever be unbalanced?: You can work it out this way: think about what torque = r × F means when r and F are equal.
Where is the center of mass of three unequal masses?: X_cm = Σ(m_i × x_i) / Σm_i.