Newton-metre

Unit of torque in the International System of Units

Diagram illustrating the concept of a newton-metre.

The newton-metre (symbol: N_m) is the SI derived unit of torque (also called moment). It is equal to the torque resulting from a force of one newton applied perpendicularly to the end of a moment arm that is one metre long.

Definition

The newton-metre is defined as the torque that results when a force of one newton is applied at a perpendicular distance of one metre from the axis of rotation. Mathematically, it is expressed as:

\( \tau = F \times d \)

where \( \tau \) is the torque, \( F \) is the force in newtons, and \( d \) is the distance in metres from the axis of rotation.

Applications

The newton-metre is commonly used in various fields of engineering and physics to quantify the amount of torque applied to an object. It is particularly important in the design and analysis of mechanical systems, such as engines, gearboxes, and other rotating machinery.

Relation to other units

The newton-metre is dimensionally equivalent to the joule, which is the SI unit of energy. However, the newton-metre is used specifically for torque, while the joule is used for energy. This distinction is important because torque and energy are different physical concepts.

Conversion

In some contexts, torque may be expressed in other units such as pound-foot (lb_ft) or kilogram-metre (kg_m). The conversion between these units and the newton-metre depends on the conversion factors for force and distance:

1 N_m = 0.737562 lb_ft

1 N_m = 0.101972 kg_m

Related pages

• Torque
• Newton (unit)
• Metre
• Joule
• SI derived unit