Answer:
Her moment of inertia decreases causing her spin to speed up. The physics law behind this phenomenon is the conservation of angular momentum.
Explanation:
<em>Theory</em>
<u>The Law of conservation of angular momentum</u>
The angular momentum of a rotating body or a system remains constant unless it is acted upon by an external unbalance force.
Angular momentum = moment of inertia × angular velocity
The moment of inertia = mass×[perpendicular distance from axis of rotation]²
___________________________________________________________
⇒When skater draws in her outstretched arms the mass distribution get concentrated towards the axis of rotation so the moment of inertia of the body decrease.
But angular moment should conserve so angular velocity increases (spin increases)