Whirlpools and physics

Manuel Ortiz Acosta

Whirlpools have been legends since the existence of human civilizations. They are well known for their power and capabilities of sinking ships and disappearing people and civilizations. Everyone fears them, for they will swallow you if you get to close. A whirlpool is a swirling body of water. This phenomenon is one of the powers that the sea possess, and so it can be destructive. 

Since early times in literature we see monsters coming out of whirlpools and swallowing entire ships and killing everyone. . In Greek mythology we can find Charybdis the daughter of Poseidon, who is just a whirlpool it appears in the poems of The Odyssey, Jason and The Argonauts, and Ovid's Metamorphoses. Is that really true? These phenomena might have  enough power to sink a ship and it’s more than enough to drown humans and other animals

This phenomena can happen for many reasons. One of this is when two currents come together, this ones are known as tidal whirlpools. They usually happen because of the force of gravity, if you do an experiment with two bottles tied together one empty and another one with water when you change the position and the one with water is up, it’ll form a whirlpool while it goes down, this is because the water is more dense than the air and the gravity force pulls it down and that is when the water starts to whirl around creating a circular motion as it goes down with centripetal acceleration.

That is what happens with the whirlpools at sea. When less dense water is over more dense water the pressure pulls the less dense water down and it start whirling around in circular motion. In the center the whirlpool has negative pressure and that’s why the center is empty. In beaches where the sea has mountains, is a more favorable condition for whirlpools to occur since when the current flows the less dense water will be automatically over the denser water and the force of pressure acts and the water starts to whirls.

The question is how we can survive a whirlpool if we can. Many persons claim to have done it. Some say they used more speed in their boats, others more weight. What pulls you to the center of the whirlpool is the centripetal force and centripetal force is directly proportional to mass and the square of velocity, and indirectly proportional to the radius(the distance to the center of the whirlpool).  This means that if you have more mass there will have to be more centripetal force to be able to pull you down to the center of the circle. That is why lighter objects go to the center of the whirlpool and heavier objects stay out. Also if you have higher speed you can also survive it, because of the same reason, the whirlpool will need more force to pull you to the center and obviously if the distance from the center is more,  there will be less force acting on the object and it’ll be easier to get out from the circular motion and survive. The whirlpool will be need more force to get the object out from the inertia state and move it. When the process of the water moving  is over, the whirlpools  disappears because there is no more force acting on it to keep it motion.

Reference

Underwater Universe. (2011). The History Channel website. Retrieved 4:42, April 15, 2011, from http://www.history.com/shows/underwater-universe/episodes/episode-guide.

Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Scylla" 1.

Giancoli, Douglas C. Physics for Scientists & Engineers with Modern Physics. 4th ed. Vol. 1. Upper Saddle River, N.J: Prentice Hall, 2009. Print.

Dr. Lu, Junquiang. Class Lecture. General Physics I. University of Puerto Rico, Mayagüez Campus. Spring 2011.