68.21 Chapter 5. Applications of Higher Order Equations. Exercises 5.3, page 249

68.21.1 problem 15
68.21.2 problem 16
68.21.3 problem 17
68.21.4 problem 18
68.21.5 problem 21 (a)
68.21.6 problem 21 (b)
68.21.7 problem 22 (a)
68.21.8 problem 22 (a)
68.21.9 problem 24