This lesson does a good job of showing how to draw and calculate forces on objects on inclines and other more complicated situations. The sample problems and the problems students work through are similar to those on the AP test. If you take your time and work through the problems yourself, without guessing or looking at the answer too soon, it should help your problem-solving skills and your understanding. It's easy to cheat on, though... self-discipline is needed. Don't go through this lesson if you're short on time...