# Torque

Torque, moment or moment of force (see the terminology below), is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. Mathematically, torque is defined as the cross product of force and the lever-arm distance, which tends to produce rotation.

Loosely speaking, torque is a measure of the turning force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.

The symbol for torque is typically τ, the Greek letter tau. When it is called moment, it is commonly denoted M.

The magnitude of torque depends on three quantities: the force applied, the length of the lever arm connecting the axis to the point of force application, and the angle between the force vector and the lever arm. In symbols:

where

τ is the torque vector and τ is the magnitude of the torque,
r is the displacement vector (a vector from the point from which torque is measured to the point where force is applied), and r is the length (or magnitude) of the lever arm vector,
F is the force vector, and F is the magnitude of the force,
× denotes the cross product,
θ is the angle between the force vector and the lever arm vector.

The length of the lever arm is particularly important; choosing this length appropriately lies behind the operation of levers, pulleys, gears, and most other simple machines involving a mechanical advantage.

The SI unit for torque is the newton metre (N·m). For more on the units of torque, see below.

### Other articles related to "torque":

Stall Torque - Hydrodynamic Transmissions
... The torque produced by a fluid coupling is maximum when the output stage is stalled (i.e ... is not rotating), the stall torque may also refer to the maximum output torque that a fluid coupling can produce without damage ... In the case of torque converters, the stall torque is close to or the same as the maximum output torque produced for a given input speed ...
Self Aligning Torque
... Self aligning torque, also known as aligning torque, SAT, or Mz, is the torque that a tire creates as it rolls along, which tends to steer it, i.e ... In the presence of a non-zero slip angle, this torque tends to steer the tire toward the direction in which it is traveling, hence its name ... The magnitude of this torque can be calculated as the product of the lateral force generated at the contact patch and the distance behind the wheel centre at which ...
Stall Torque - Electric Motors
... Electric motors continue to provide torque when stalled ... The maximum torque an electric motor can produce in the long term when stalled without causing damage is called the maximum continuous stall torque ...
Stall Torque
... Stall torque is the torque which is produced by a device when the output rotational speed is zero ... It may also mean the torque load that causes the output rotational speed of a device to become zero - i.e ... This condition occurs when the load torque is greater than the motor shaft torque i.e ...
Torque Multiplier
... A torque multiplier is a gear box with reduction ratios greater than 1 ... The given torque at the input gets multiplied as per the reduction ratio and transmitted to the output, thereby achieving greater torque, but with reduced rotational speed ...

### Famous quotes containing the word torque:

Poetry uses the hub of a torque converter for a jello mold.
Diane Glancy (b. 1941)