angular momentum

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.