Carefully read example 5 on page 569, and then do problems 49 through 52 on page 571.
Read problem 63 on pages 571 - 72 about the design of a suspension bridge, and play with the parabola that is described in the problem. See if you can understand what the problem is asking. Or, if you prefer, try Problem 64 about a bridge arch. These problems are best done with several students together.
If you are having problems with 11 - 29, look at example 3 on page 568.