10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. How would you convince a relative who had not studied physics that the moon is really a falling body? A typical neutron star has a mass of 3.98 x 103\" kg and a radius of 12.0 km. What is the gravitational acceleration at the surface? When a star like the Sun has exhausted most of its fuel, it expands into a red giant, with a radius approximately equal to the orbit of Earth, an increase of about 216 times. By what factor does its surface gravity change, assuming that the mass remains constant? Ceres is a dwarf planet with a surface gravity of 0.27 mfsz, and a mass of 7.0 x lmkg. What is its radius? You are located a distance r from a planet with mass m, and feel a gravitational force FE. Later, you find yourself a distance of 4r from a planet with a mass of 8m. How does the gravitational force from the second planet compare with that from the first? Mikhail says, "since the mass of Earth is much greater than my mass, the force that Earth exerts on me is much greater than the force I exert on Earth." Is he correct? Explain your answer. Explain why Henry Cavendish used a light beam to measure the gravitational force between two lead spheres rather than a spring balance. When working out physics problems involving the gravitational acceleration at the surface of Earth, the value of g is usually given to 2 or at most 3 significant digits, although modern methods of measurement allow much greater accuracy. Why is this? One of the early communications satellites was Telstar, launched in 1962 and inspiring a popular song on the radio. It followed an elliptical orbit that varied from about 100 X 103 km to 6.00 X 101 km above Earth. What was its orbital speed at its closest approach to Earth? G\": r for a satellite? Under what conditions may you use the equation 1: = Why are some satellites put into geostationary orbits while others are not? The farthest distance that a planet could be from the sun, and still orbit the sun, is usually considered as halfway to next nearest star, Proxima Centauri, which is about 2.15 light-years, or 4 0'? x 1016 to distant. What is the orbital speed of such a planet? What information in this chapter did you find related closely with an activity that you enjoy? How did studying this information change your outlook on that activity? The star Cygnus X-l is orbiting its unseen companion, likely a black hole, at a distance of about 3 0 x 1010 m with a period of about 5.6 Earth days. Miat is the orbital speed of the star? The star Cygnus X-l is orbiting its unseen companion, likely a black hole, at a speed of about 3 9 x lo: rats at an orbital radius of about . What is the mass of the black hole