A chain that speeds up, rather than slows, due to collisions: How compression can cause tension

When two nominally rigid objects collide, their velocities change in response to the compression force between them. The difference in the normal component of the velocities of the objects is thus generally eliminated or reversed. The nature of collisions for nonrigid objects is more subtle. Surprisingly, when a long chain moving lengthwise collides with a wall, the chain can be pulled into the wall (instead of pushed away) with the approach velocity between the wall and chain increasing in time rather than not changing or decreasing. We discuss theoretical limits on how much a chain can be pulled into an object with which it collides, some chain link designs that lead to these limits, and experimental results which show the pulling of one of these chain link designs into a wall.