The lever of strength. Definition and calculation examples

M = FL

F is the force vector, [N];

L – lever strength, [m];

M is the moment of force, [Nm].

It is determined by the long normal (perpendicular) to the line of effort drawn from the point in question.

AB is the lever.

It is designated: L, l or h. Measured in meters [m].

The arm of force is one of two factors determining the moment of force.

Our short video tutorial about the moment and lever with examples:

We can speak about the lever of force only when there is a direct connection between the force and the point relative to which the moment arises.

The order of finding the lever strength

Consider the order of finding the lever of force F with respect to point A.

To do this, we show the line a, in the direction of the force F

From point A, drop the perpendicular to the line a.

The length of this perpendicular is the lever of strength.

Examples of determining lever strength

1. The force is perpendicular to the axis of the rod and the distance between points A and B is known.

The arm of the force with respect to point A is equal to the length of the segment AB.

2. The force is located at a certain angle to the axis of the rod

The arm of the force relative to point B is AB×cos30°

3. The distance from the point to the line of action of the force is known.

The leverage of the force relative to point B is 3m.