For a balanced object (equilibrium):
This is called the principle of moments.
See-saw Example:
Person A (60 kg) Person B (40 kg)
↓ ↓
●━━━━━━━━━━━▲━━━━━━━━━━━━━━━━●
|←— 2 m —→|pivot|←—— ? m ——→|
For balance: Clockwise moment = Anticlockwise moment
60 × 10 × 2 = 40 × 10 × d
1200 = 400 × d
d = 3 m (Person B sits 3 m from pivot)
Quick Check: A spanner applies a force of 40 N at a perpendicular distance of 0.25 m from a bolt. What is the moment?
M = F × d = 40 × 0.25 = 10 Nm. Remember: distance must be perpendicular to the force direction.
This key facts covers The Principle of Moments within Moments & Levers for GCSE Physics. Revise Moments & Levers in Forces for GCSE Physics with 13 exam-style questions and 10 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 14 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Moments & Levers
What is a moment?
State the principle of moments.