Answer:
90°
Explanation:
The angle will be 90° when momentum for a system can be conserved in one direction while not being conserved in another.
The example can be
If we apply force on an object horizontally in west direction, then as in other direction south or north we cannot apply the principal of momentum conservation.
Answer:

Explanation:
Assume both children bodies are point particles. The total moment of inertia about the rotation axis of 2 points particles of mass 16 kg and 25 kg at 1.5 m arm length is

where
are the masses of 2 children
are their distance to the center of rotation
