Answer:
Angular speed would increase, assuming that angular momentum is conserved.
Explanation:
The angular momentum [tex]L[/tex] of an object is the product of its moment of inertia [tex]I[/tex] and its angular velocity [tex]\omega[/tex]:
[tex]L = I\, \omega[/tex].
Let [tex]\omega_{0}[/tex] and [tex]\omega_{1}[/tex] denote the angular speed of the cloud before and after the change. Let [tex]I_{0}[/tex] and [tex]I_{1}[/tex] denote the moment of inertia before and after the change.
If angular momentum is conserved:
[tex]I_{0}\, \omega_{0} = I_{1}\, \omega_{1}[/tex].
[tex]\displaystyle \omega_{1} = \left(\frac{I_{0}}{I_{1}}\right)\, \omega_{0}[/tex].
In other words, under the assumption that angular momentum is conserved, angular velocity after the change would be proportional to [tex](I_{0} / I_{1})[/tex], the ratio between the previous and the current moment of inertia.
The moment of inertia of a rotating object is usually proportional to the square of radius. For example, if the cloud can be approximated as a disk of mass [tex]m[/tex], radius [tex]r[/tex], and uniform density rotating along the central axis, moment of inertia would be [tex]I = (1/2) \, m\, r^{2}[/tex].
Since the radius of the cloud is reduced during this change, moment of inertia of the cloud would also become smaller. The ratio [tex](I_{0} / I_{1})[/tex] would be greater than [tex]1[/tex], such that [tex]\omega_{1} > \omega_{0}[/tex].
In other words, the angular speed of the cloud would likely increase during this change.
