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Chapter 4- Diving Science Diving Science 97 Your body is transferring heat to the water touching your body to try to get the water as warm as you are. When your body is drained of enough heat, you will be chilled and start to shiver. Shivering is your body’s signal to tell you that it can no longer generate enough heat to keep your internal organs warm. When you start to shiver on a dive, you must end your dive and get out of the water to rewarm. Drag Have you ever tried to run in water even up to your waist? If so, you know how difficult it is compared to running in air. The water resists your movement. This resistance to movement is called drag. Drag is something that you must deal with when diving. The total frontal area of your body and equipment and its surface configuration also affect your resistance to movement in the water. If your equipment is sleek and compact, it will be easier for you to swim than if your gear has dangling hoses and loose straps. The more you can streamline yourself and your equipment, the easier it will be for you to move through the water. If you are in a horizontal position, you have much less resistance to forward movement than if you are in a semi-upright position (figure 4-6). Verify What You Have Learned Review the following questions about density and its effects: 1. Air is approximately __________ oxygen and 78% _________________. 2. True or false: Air is denser in the mountains (at altitude) than at sea level. 3. True or false: Water is denser at 30 meters (99 feet) than it is at 3 meters (10 feet). 4. One way you can reduce drag under water is by ____________________________. 5. When you look at objects under water, they appear ____________________ and _______________ than they really are. 6. True or false: Sound travels slower under water. FIGURE 4-6. STREAMLINING YOUR EQUIPMENT AND YOURSELF MAKES IT MUCH EASIER TO MOVE THROUGH THE WATER. BUOYANCY When different objects are placed in water, some float, some sink, and some remain suspended between the surface and the bottom. These objects all have varying densities and this affects their buoyancy. By understanding buoyancy, you can control it to your advantage for diving. Archimedes Principle Archimedes, a Greek philosopher, noticed that the level of water in a tub rose when he sat in it. From that observation and other experiments, he found that an object in a fluid is buoyed up (lifted) by a force equal to the weight of the fluid it displaces.


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