Sentence:  Secondly, When a body is once in motion it will continue to <WSD>move</WSD> forever, unless something stops it. When a ball is struck on the surface of the earth, the friction of the earth and the resistance of the air soon stop its motion. 
Meaning of the word marked with <WSD> tags:  To change place or posture; to go, in any manner, from one place or position to another.