Question

when considering how a force affects motion, identify the object(s) of interest as the
and then identify the force(s) exerted on the
by the external world.

Explanation:

In physics, when analyzing the effect of forces on motion, the object(s) of interest is called the system. Forces exerted on the system by the external world are external forces. This is a fundamental concept in understanding motion and forces.

Answer:

system; system