Atrast vala. Welcome to my little sanctuary. My name is Sean and I am from Kent, Washington (US). I hope you enjoy your visit to my blog. If you ever need anything or just want to talk, drop me an ask.
It is a magnet that is pulling one piece of the putty closer, while the bulk is farther away and, as a result, the magnetic field is weaker and not pulling all of it equally. The putty consistency (and I imagine the magnetism within the putty) makes it so that the putty won’t just split, making the middle area thinner as it pulls material trying to reach the magnet.
Additionally, since magnetic field strength is also related to velocity, this means that the faster things are moving, the stronger the field, which is why it seems to speed up when it gets close as well as how it can maintain its upward motion as the magnet is accelerated.