گالیله و قانون اینرسی (Galileo and Inertia)

An object's velocity will not change all on its own.

Pushes, or pulls, are necessary to change an object's velocity.

Therefore:

Pushes, or pulls, are not necessary to keep an object moving.

An object will keep moving all on its own.

گالیله و قانون اینرسی (Galileo and Inertia)