.Reviewing Main Ideas 1 . Explain how the force due to gravity keeps a satellite in orbit. 2. Is there gravitational force between two students sitting in a classroom? If so, explain why you don't observe any effects of this force. 3. Earth has a mass of 5.97 x 1024 kg and a radius of 6.38 x 106 In, while Saturn has a mass of 5.68 x 1026 kg and a radius of 6.03 x 107 In. Find the weight of a 65.0 kg person at the following locations: a. on the surface of Earth b. 1000 km above the surface of Earth c. on the surface of Saturn d. 1000 km above the surface of Saturn 4. What is the magnitude of g at a height above Earth's surface where ee- fall acceleration equals 6.5 Ill/82? d Critical Thinking 5. Suppose the value of G has just been discovered. Use the value of G and an approximate value for Earth's radius (6.38 x 10'5 m) to nd an approxi- mation for Earth's mass. Circular Motion and Gravitation 237