Conversion for torque
The unit for the moment (torque) is derived from the basic units "force" and "distance".
If the force acts on a rigid body with a fixed axis of rotation, then this body is not displaced but set in a rotary motion.
In this case, not only the magnitude of the force, but also the distance of the force application point to the axis of rotation is important: the greater the distance, the greater the rotary effect (rotational acceleration).
The moment is defined by force times the lever arm.
The rotary motion is also influenced when a pair of forces acts on a rigid body instead of a single force.
A pure rotary motion - without displacement - occurs when the two forces act in opposite directions and are of equal magnitude.
This pair of forces is always present with a moment (torque): In a rotatably mounted body on which a force acts, the bearing reaction force forms the opposite force, which is exactly the same magnitude and acts at a certain lever distance.
You could therefore say: A moment is a pair of forces.
In technology, a distinction is made between:
- Drive torque (for a machine that delivers power),
- Output torque (for a machine that consumes power).
If the force pair (moment) does not trigger a rotational movement, we do not speak of torque but of moment. Depending on the type of mechanical load, a technical distinction is made between:
- Bending moment,
- Torsional moment.
The unit Newton meter for moment (torque) is derived from the Si units for force (Newton) and length (meter).
