Figure 8.1  The work done by an external agent on the system of the book and the Earth as the book is lifted from a height ya to a height yb is equal to mgyb – mgya. Fig. 8.1, p.218

Figure 8.2 The work done by the gravitational force on the book as the book falls from yb to a height ya is equal to mgyb – mgya. Fig. 8.2, p.220

Figure 8.10  The loss in mechanical energy due to the force of kinetic friction depends on the path taken as the book is moved from A to B. The loss in mechanical energy is greater along the red path than along the blue path. Fig. 8.10, p.229

Fig. P8.24, p.243