Active Figure 13.1  The gravitational force between two particles is attractive. The unit vector r12 is directed from particle 1 toward particle 2. Note that F21 = – F12. At the Active Figures link at http://www/pse6.com, you can change the separation distance between the particles to see the effect on the gravitational force. Fig. 13.1, p.391

Figure 13.2  As it revolves around the Earth, the Moon experiences a centripetal acceleration aM directed toward the Earth. An object near the Earth’s surface, such as the apple shown here, experiences an acceleration g. (Dimensions are not to scale.) Fig. 13.2, p.392

Astronauts F. Story Musgrave and Jeffrey A Astronauts F. Story Musgrave and Jeffrey A. Hoffman, along with the Hubble Space Telescope and the space shuttle Endeavor, are all in free fall while orbiting the Earth. p.394

Figure 13.4  Schematic diagram of the Cavendish apparatus for measuring G. As the small spheres of mass m are attracted to the large spheres of mass M, the rod between the two small spheres rotates through a small angle. A light beam reflected from a mirror on the rotating apparatus measures the angle of rotation. The dashed line represents the original position of the rod. Fig. 13.4, p.393

Table 13.1, p.395

Table13. 2, p.399

Figure 13.9 A satellite of mass m moving around the Earth in a circular orbit of radius r with constant speed v. The only force acting on the satellite is the gravitational force Fg. (Not drawn to scale) Fig. 13.9, p.401

Figure 13.10  (a) The gravitational field vectors in the vicinity of a uniform spherical mass such as the Earth vary in both direction and magnitude. The vectors point in the direction of the acceleration a particle would experience if it were placed in the field. The magnitude of the field vector at any location is the magnitude of the free-fall acceleration at that location. (b) The gravitational field vectors in a small region near the Earth’s surface are uniform in both direction and magnitude. Fig. 13.10, p.402

Figure 13.12  As a particle of mass m moves from A to B above the Earth’s surface, the gravitational potential energy changes according to Equation 13.11. Fig. 13.12, p.403

Figure 13.13  Graph of the gravitational potential energy U versus r for an object above the Earth’s surface. The potential energy goes to zero as r approaches infinity. Fig. 13.13, p.404

Figure 13.16  An object of mass m projected upward from the Earth’s surface with an initial speed vi reaches a maximum altitude h. Fig. 13.16, p.407

Table 13.3, p.408

Figure 13.3  The resultant gravitational force acting on the cue ball is the vector sum F21 + F31. Fig. 13.3, p.393