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Water is obviously different from air in many ways, but what differences should be noted in order to help us become efficient, effective swimmers? One of the primary contrasts between air and water are their respective densities. When we place water and air side by side with the same volume, water has more weight and far more viscous (thicker) than water. This is the very reason as to why humans move through air and water using different methods. When we walk through land, the main force opposing our motion is gravity, and our body has to compensate to keep you from toppling over and maintaining your balance. Although very natural, our body lifts our legs from the ground and swings our arms to oppose the force of gravity. However, in water, gravity is cancelled out because of buoyancy, which is our tendency to float in fluid. Instead of gravity being the main opposing force, the major force that swimmers have to work against is the drag, or otherwise known as water resistance. Also, another obstacle we swimmers face is the coldness of the water. Since water is more dense, it has the ability to remove heat from our bodies 25-40 times faster than air of the same temperature; hence why surfers wear wetsuits to avoid hypothermia, the deadly, rapid cooling of the human body. Additionally, due to the waters' density, it takes time to warm up, which is why beach temperatures are the warmest 2-3 months after summer. (Woodford)
Density (p) = mass x volume
Viscosity: internal resistance to flow (Schneider)
Density (p) = mass x volume
Viscosity: internal resistance to flow (Schneider)
Water Movement
As the body goes forward, water is then given a momentum from the arm/kick motion and continues to travel in the opposite direction from the swimmer until its velocity hits 0. If there are 2 people swimming in one lane with in front of the other, the person in the back has to exert less work because they are being pulled by the swimmer due to a small drag from the swimmer in front. When the swimmer behind places his or her arm in the water for the power phase, the water in which they are placing their hands in already has momentum in it, therefore making it easier for the swimmer behind to travel the same distance. (Woodford)
Cool fact: What is the purpose of swimming lanes?
Even at your local outdoor pool, you might have seen floating lane lines. Swimmers are often told to "keep right", and so the swimming circuit goes in a counterclockwise motion. Lanes minimize the waves created by swimmers by knocking them down, as well as minimizing the momentum of the water as produced by the swimmers themselves. (Woodford)
Even at your local outdoor pool, you might have seen floating lane lines. Swimmers are often told to "keep right", and so the swimming circuit goes in a counterclockwise motion. Lanes minimize the waves created by swimmers by knocking them down, as well as minimizing the momentum of the water as produced by the swimmers themselves. (Woodford)