torque

is often called a moment, can informally be thought of as "rotational force" or "angular force" which causes a change in rotational motion. This force is defined by linear force multiplied by a radius.

The SI unit for torque is the newton metre (N m). In U.S. customary units, it is measured in foot pounds (ft·lb_f) (also known as 'pounds feet'). The symbol for torque is τ, the Greek letter tau.

Definition

Angular momentum of a particle about some origin is defined as:

where:

is the angular momentum of the particle,

is the position of the particle expressed as a displacement vector from the origin,

is the linear momentum of the particle, and

is the vector cross product.

The angular momentum are newton-meter-seconds; N·m·s (kgm²s^-1).

Because of the cross product, L is a pseudovector perpendicular to both the radial vector r and the momentum vector p.

If a system consists of several particles, the total angular momentum about an origin can be obtained by adding (or integrating) all the angular momenta of the constituent particles. Angular momentum can also be calculated by multiplying the square of the displacement r, the mass of the particle and the angular velocity.

Also see torque converter.

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