Adriver drives 3 blocks north, 3 blocks east and 3 blocks south. what is the total displacement?

The 3 blocks north and the 3 blocks south cancel each other, and contribute nothing to the displacement.  The total displacement is 3 blocks east.

measuring things 1 litre of water

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach