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Note, that the above calculation can also be performed per mass, using [[kinematics]] only. Thus the phenomena of figure skater accelerating tangential velocity while pulling their hands in, can be understood as follows in layman's language: The skater's palms are not moving in a straight line, so they are constantly accelerating inwards, but do not gain additional speed because the accelerating is always done when their motion inwards is zero. However, this is different when pulling the palms closer to the body: The acceleration due to rotation now increases the speed; but because of the rotation, the increase in speed does not translate to a significant speed inwards, but to an increase of the rotation speed.
==== Conservation of Momentum Definition is not Perpetual Motion ====
<small>The above equation:</small>
<small>(1) <math> 0 = dL = d (I\cdot \omega) = dI \cdot \omega + I \cdot d\omega </math> means theoretically:</small>
<small>(2) <math> dL=0 </math></small>
<small>Which itself means <math> L </math> not changing and thus:</small>
<small>(3) <math> L_1=L_2 </math></small>
<small>That is, given two distinct moments in time <math> t_1 </math> and <math> t_2 </math> during some object rotation, <math> L </math> will stay the same.</small>
<small>The interval <math> t_2 - t_1 </math> is arbitrary, also indefinitely long, where conditions (1), (2) and (3) are met: meaning <math> L </math> could not change for an infinite amount of time which resembles perpetual motion, impossible by definition.</small>
<small>Thus the scientific and realistic definition of Momentum Conservation is not (3) but:</small>
<small>(4) <math> L_1 \to L_2 </math></small>
<small>Which express the ''tendency'' of any moving object to preserve its motion, as previously stated.</small>
<small>From a logical perspective "conservation" means equivalence between to states, thus "=", and not a tendency "<math> \to </math>": but given the fact that a perpetual motion scenario is self excluding, "Momentum Conservation" is a commonly accepted definition instead of the exact "Tendency to Momentum Conservation".</small>
=== Stationary-action principle ===
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