1. The document discusses geosynchronous and geostationary orbits. A geosynchronous orbit has the same period as Earth's rotation (24 hours), while a geostationary orbit is directly above the equator. Geostationary satellites remain stationary above the same point on Earth. 2. It also describes weightlessness experienced by astronauts. In orbit, astronauts feel weightless because the satellite provides an outward centrifugal force equal to Earth's inward gravitational force, so there is no net force felt. 3. The Global Positioning System (GPS) uses 24 satellites to enable devices to calculate location via triangulation of signals. GPS is used for navigation, mapping, and other applications both military and civilian.