Falling rapidly towards the ground is usually bad news. But put a slide beneath you, and you're guided to a safe landing. Pools and water parks take this to an extreme, with long, elaborate slides that descend several stories.
How do engineers decide how strong these slides need to be? The slide, and the structure supporting it, must always push against you with enough force to propel you through its twists and turns. If not, the slide collapses, which would take the fun out of the whole ordeal.