hoekmoment

Hoekmoment, in physics often called angular momentum, is a measure of the rotation of a system. It is a vector quantity defined for a system of particles as L = Σ r_i × p_i, where r_i is the position of a particle relative to a chosen origin and p_i its linear momentum. For a rigid body, L can be written as L = I · ω, with ω the angular velocity and I the inertia tensor, indicating how mass is distributed relative to the rotation axis.

Dynamics of rotation are governed by torque: τ = dL/dt. In the absence of external torque about a chosen origin, the angular momentum is conserved. This conservation applies in many contexts, such as planetary motion or a rotating figure skater pulling in their arms to increase spin.

Hoekmoment can be decomposed into orbital angular momentum, arising from the motion of mass relative to a point, and spin angular momentum, which is intrinsic to particles. The total angular momentum of a system is the sum of its orbital and spin components, and it is important in both classical and quantum descriptions of rotational motion.

Units and and magnitude: SI units are kilogram meter squared per second (kg·m^2·s^-1). The direction of hoekmoment follows the right-hand rule: it points along the axis about which the body tends to rotate.

In quantum mechanics, angular momentum is quantized. The eigenvalues of L^2 are l(l+1)ħ^2, and the eigenvalues of a chosen component, such as L_z, are mħ. Spin angular momentum is intrinsic to particles and combines with orbital angular momentum to form total angular momentum.