High School Physics

Moment meaning in physics

Sometimes a force causes an object to rotate or turn. A moment is a measure of the turning effect of a force.

Factors affecting Moment or turning effect

The turning effect depends on two things:

  • the magnitude of the force applied
  • the perpendicular distance of the force from the pivot.

What is Pivot

A pivot is a point around which rotational movement takes place.

Moment Formula

moment = force × perpendicular distance from the pivot
M = F × d
Here, M = moment (N m)
F = force (N)
d = perpendicular distance from the pivot (m)

Moment Unit in SI

The unit of Moment in SI is Newton meter (N m).
[Note: The unit of force is the newton (N) and the unit of distance is the meter (m).]

Moment example [Spanner use]

The moment is greater if either F or d is increased. For example, to undo a tight nut with a spanner, you need a large moment.
This can be achieved by applying a large force with a spanner.
If a longer spanner is used, a smaller force is needed and it is much easier to undo the nut. The force is applied at a greater distance.

Moment example [Spanner use]

More Examples, where moments are important, include:

  • door handles
  • see-saws
  • cranes
  • levers.

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