How can a horde of active robots be automatically brought to a standstill? By arresting their dynamics in a self-sustained way. This phenomenon was discovered by physicists at Heinrich Heine ...

1.1 What is friction? Take this everyday example: when a coffee mug rests on a flat table, the kinetic frictional force is zero. There is no force trying to move the mug across the table, so there is ...

Imagine a heavy book resting on a table. If you try to gently push the book across the table with the tip of your finger, it may first appear to remain motionless—it needs a lot more force to start ...

Probably everyone is familiar with the phenomenon: water drops cling to a pane of glass, if it is tilted out of the horizontal plane. Only when a certain angle is reached they slide off. This raises ...