4. MOMENTS - THE TURNING EFFECTS OF FORCES

4. MOMENTS - THE TURNING EFFECTS OF FORCES
Key notes
1. The moment of a force means the turning effect of a force.
2. The principle of moments states that for an object in equilibrium, the sum of
all clockwise moments = the sum of all anticlockwise moments.
3. Levers use the principle of moments.
4. If the distance of the effort from the fulcrum is greater than the distance of the
load from the fulcrum, then a small effort can be used to lift a heavy load.
5. The centre of gravity of an object is the point where its whole weight seems to
act.
6. When an object is hung freely, its centre of gravity is located vertically below
the point of support.
7. An object is in a stable equilibrium if its centre of gravity is raised when tilted
and it returns to its initial position when released.
8. An object is in unstable equilibrium if its centre of gravity is lowered when the
object is tilted and it topples over to a new position when released.
9. An object is in a neutral equilibrium if its centre of gravity is not raised or
lowered when displaced.
10. The stability of an object increase if its centre of gravity is lower or its base
area is increased
Formulas:
 Moment = F x d
= force x perpendicular distance from the pivot to the force
Units is Nm (newton metre)