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Moments

What you need to know

Reflections and Exam tips

 

Moments

The turning effect of a force is called the MOMENT which can be increased by:

  1. increasing the size of the force
  2. increasing the distance from the pivot to the line of action of the force (using a longer instrument)

Equation:

Moment (Newton metres, Nm)= force (Newtons, N) x perpendicular distance from pivot (Metre, m)

Example: Levers reduce the force needed to perform tasks such as lifting a heavy object.
When a lever is used a force (Effort) is exerted around a Pivot to move an object (Load).

 

Less force is needed to open a door by pushing at the side furthest from the hinge than at the side closest to the hinge as there is greater momentum.

Balancing moments

If an object is not turning around a pivot, the total clockwise moment is balanced by the total anti-clockwise moment.
The opposing moments are balanced:

sum of the clockwise moments = sum of the anti-clockwise moments

Example using a see-saw:

  1. the person on the right exerts a force downward - which causes a clockwise moment
  2. the person of the left exerts a force downward - which causes an anti-clockwise moment