(3-7) Have a look at the three graphs below, which show the variation of force with distance.

①  Graph A shows the simple situation of a constant force. In this situation,   W = FΔx, where Δx is the change in x-coordinate. If we want to know the work required to change the x-coordinate from 10m to 40m, we can easily calculate it from this formula. How does this relate to the graph?

②  Graph B shows a force that decreases linearly with distance. Again, figure out the work needed to change the x-coordinate from 10m to 40m (the key this time is to think about the mean force over this distance range).

③  Graph C introduces the idea of breaking down the movement into stages. Use the same method to deduce the work done in each of these stages, and hence show that this is an alternative way to evaluate the overall work done.