# angular momentum

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## angular momentum

MRI
The cross product of the ordinary momentum of a particle and its position vector, running from the axis of rotation to the body whose momentum is being determined.

In absence of external forces, the angular momentum (AM) remains constant; therefore, a rotating body tends to maintain the same axis of rotation. When torque is applied to a rotating body, the resulting change in AM results in precession. Momentum involved in the rotation of a body about an axis is conserved, as is ordinary momentum. Atomic nuclei possess an intrinsic AM known as “spin”, which is measured in multiples of Planck’s constant.

## an·gu·lar mo·men·tum

(ang'gyŭ-lăr mō-men'tŭm)
The spin of MR active nuclei, which depends on the balance between the number of protons and neutrons in the nucleus.

## momentum

the 'quantity of motion' of a body or object. A vector quantity. linear momentum the product of mass and velocity. The change in linear momentum is equal to the linear impulse. conservation of linear momentum in the absence of external unbalanced forces, the total linear momentum of colliding bodies or objects will remain constant. Commonly applied to racquet/ball impacts. angular momentum the product of moment of inertia and angular velocity. conservation of angular momentum in the absence of an external moment (torque), the angular momentum of a rotating body will remain constant. Often applied to low-velocity flight (e.g. gymnastics) to explain how a body can increase or decrease angular velocity by manipulating moment of inertia (e.g. by 'tucking'). trading of angular momentum if, in the absence of an external moment (torque), an object or body is rotating about one axis (e.g. somersaulting) and rotation about another axis is introduced (e.g. tilt), the result will be a rotation about a third axis (e.g. twist) due to the vector nature of angular momentum. transfer of angular momentum can occur from one part of a body to another in the absence of an external moment (torque) (e.g. if one part of a body increases angular velocity, another part must decrease to conserve angular momentum).
References in periodicals archive ?
Mechanisms used by the support leg to regulate forward angular impulse during backward fall recovery require further investigation.
Understanding the regulation of backward angular impulse by generating forward angular impulse allows clinicians with basic knowledge to explore new therapy strategies to improve backward recovery.
Multijoint control of the swing and support legs is important in regulating the magnitude and direction of the angular impulse generated about the COM.
An individual can generate needed backward angular impulse for a forward fall recovery by generating a set of relatively large hip extensor NJMs and small knee extensor or knee flexor NJMs by activating the gluteus maximus and hamstrings.
Lower extremity control and dynamics during backward angular impulse generation in forward translating tasks.
Regulation of forward angular impulse in tasks with backward translation.

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