PHYSICS BEHIND WHIRLPOOLS

When the water begins to move in a circular motion, there will be a force pushing it outwards. Well, we SAY that, but really it is simply the force of inertia that makes it go in a straight line, so, when you try to move the water, all of the water molecules 'try' to go off in a tangent from wherever they are.

This creates a net outward force, what we often call a centrifugal force. If there were no gravity, the water would simply form a larger and larger hole in the body of water. There would be no limit to how large the hole could get!

Gravity acts on the water and creates a pressure that is proportional to how much water is above it; that is, the deeper you go, the higher the pressure. And this varying pressure is pushing against the force of the outward pressure caused by the rotation.

So now we have a situation where the rotation forces the water outwards and gravity increases the water pressure. The water pressure pushes against the force of the rotation and forces the water back towards the centre of the rotation, but proportional the depth. So the deeper the water is, the more pressure the water exerts - because of gravity - and the more the water is able to overcome the rotational force and move towards the centre of the vortex. And of course, higher up, where there is less pressure, the water is more thrown out to the perimeter of the rotating mass of water, leaving a larger hole.

If the water is deep enough, there will always be a point, a depth, where the water pressure caused by gravity will just balance the - for each speed - the rotational force (centrifugal force), and that will be the bottom of the vortex. Below that, the pressure will always overcome the outward force caused by the rotation.

Made byVihaan Kohli7 –B