Question
Wed November 23, 2011 By:

plz explain torque

Expert Reply
Thu November 24, 2011
Torque, moment or moment of force is the tendency of a force to rotate an object about an axis or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.
The symbol for torque is typically ?, 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:

torque = r x F
? = rF Sin?

where

? is the torque vector and ? 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,
? 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).

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