Why does water flush clockwise

Now wait a few minutes until the water is hardly moving and then open the drain. Students will then notice how the water ends up swirling down the drain in the same direction that they stirred it earlier.

Repeat the experiment stirring counterclockwise. Students should conclude that the water swirls down the drain in the same direction that it was initially moving. Do you have extra time to fill? Ha ha. If so, repeat the investigation waiting longer after stirring for the water to settle. Thus even the slightest, imperceptible movement will get amplified into fast swirling.

The reason this happens is the same as why a spinning ice skater will spin faster as she pulls in her arms and legs see Figure 3. It has to do with a quantity known as angular momentum. The angular momentum is the product of three quantities: the mass of the object, the size of the object, and the spinning speed. For an object moving around in a circle, like a ball on a string being twirled around, the size in this case would refer to the distance of the ball from the center of the circle, i.

Keep that in mind when we get back to the swirling water. One last bit of terminology: When something stays the same, scientists say it is conserved. So the idea that the angular momentum stays the same is known as the conservation of angular momentum. Ask students: When the spinning ice skater starts to pull in her arms and leg, which of those change and which stay the same?

Does her mass change? Does her size change? Suppose excluding units for now , that the mass, size, and speed have these values:. What happens to her speed? The product of all three quantities must remain at 48, so. What number could the speed be that would make the product of all three numbers equal to 48? So the speed increased from 2 to 4.

Notice that when the size was divided by 2 from 6 to 3 , the speed was multiplied by 2. If the size had been divided by 3, the speed would have been multiplied by 3. The Coriolis force is in the same family as the centrifugal force. It is an inertial force caused by the rotation of an object. It is not imaginary or fictional , but is very real in the rotating reference frame.

The Coriolis force tends to make things on the surface of the object to spiral a certain direction. As the earth rotates, this motion causes everything on the surface to experience the Coriolis force, including the water in your sink.

But, the Coriolis force is so weak that it doesn't really do anything until it acts on a lot of material. A few years later, another research team at the University of Sydney showed the opposite to be true in the Southern Hemisphere. But when it comes to which direction flushed toilet water drains, only one thing matters do your flush jets point to the left or the right? Live Science. Joseph Castro.