Sentence:  If such is the case , the particles within a distance of about * * f <WSD>km</WSD> of the Earth will have , relative to the Earth , a kinetic energy less than their potential energy and they will be captured into orbits about the Earth . 
Meaning of the word marked with <WSD> tags:  a metric unit of length equal to 1000 meters (or 0.621371 miles)