What is the necessary condition for the conservation of angular momentum

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

Several mountains together form a mountain . a few of these combined form a mountain system. several systems combined form a mountain , which can stretch thousands of miles in length.

Which features on mars point to the possibility of liquid water on the planet? impact craters with sharp rims volcanic cones with craters gullies and stream-like channels mountain ranges with faults