Question

You wash the dishes. when you let the water down the drain, where is the water flowing the fastest?

Answer 1

The water flows the fastest at the center.

This is due to the friction between the water and the sink/drain. The outer parts of the water that are in contact with the kitchen sink/drain experience a greater frictional force and slow down. Their slowing down also affects the layers of water molecules adjacent to them, thereby reducing their speed as well. The layer of water molecules least affected by the friction with the sink/drain is at the center, and so they are the ones that move the fastest.