If you still don't understand collisions enough, here's a quick rundown: there are layers and masks. Masks detect layers of the same value.
1. Mask of 1 will collide with layer 1, but not anything else.
2. An object with a mask but with no layers will get easily stopped and pushed around by other objects with a layer the same value as mask
So for your game, you could have the vacuum be all 5 masks at the start (from small to big) and different objects to be different masks AND the same value layer, depending on size as well. Once the vacuum grows, change the smallest mask into a layer of the same value.
If im not completely insane, this should make that vacuum pushes objects smaller than it is, but also get stopped by objects bigger.