A Boomerangs come back because it's able to describe a circular trajectory or path. These involves two different forces.

At the instant you throw it, it start to spin. When a boomerang spins, as a gyroscope does, it creates an angular momentum. There are the force due to angular moment an the force gravitational. Two forces make a cuple that will do it rotate. The trajectory won't be an stright line.

The other force is due to different pressions betweeng upper and lower surfaces.

• - Plygoog 3 or 4 mm thickness, although 5 mm could be possible.

Boomerang collection.