Drag Racing in the Water
AbstractIt's fun to go swimming! To feel the power of your body as you launch yourself into the water. But did you know that swimming isn't just about skill and athleticism? The human body consists of skin, contours, and curves. How the water moves along your body and the clothing you are wearing determines how fast you can go. In this science fair project, you will investigate the effects of a force called drag. You will compare the time it takes to swim 25 meters in a swimsuit versus swimming the same distance in street clothing. So warm up, suit up, and get ready to dive in!
Michelle Maranowski, PhD, Science Buddies
To determine the difference in time it takes to swim 25 meters (m) in street clothing, compared to while wearing a swimsuit.
The field of biomimetics is a science based on nature, to improve human life. The word biomimetic is derived from bios, meaning "life," and mimesis, meaning "to imitate." One example of biomimetics that many of us are familiar with is Velcro®. Velcro was developed in 1941 by George de Mestral. After coming home from a trip with his dog, he noticed burrs sticking to him and to his dog's fur. He looked at the burrs under a microscope and noticed that the tips of the burrs were curved. These curved tips caught anything that had tiny loops, including clothing and fur. After a few years of research, de Mestral developed Velcro. Velcro consists of two strips of nylon, one with loops and the other with hooks.
A company that has looked to nature to get ideas is Speedo®. Speedo designs and manufactures swimsuits. Speedo looked to the shark to find out what it is about shark skin that makes the shark move so fast. It turns out that shark skin is made up of denticles that force the water into a tubular flow. This separates the shark from the water and reduces drag so that the shark can swim fast.
What is drag? Drag is a mechanical force that is generated by the interaction and contact of a solid body with a fluid. The fluid can be a liquid or a gas. Drag is also the resistance to the motion of a solid body through a fluid. Engineers who design cars and airplanes always test their designs to see how drag affects the movement.
But what does drag have to do with swimming fast? Human skin and hair interact with water and generate drag that will slow a swimmer down. Speedo has designed suits that reduce drag on the swimmer's body, and repel water. This adds up to faster swim times. In fact, many of the swimmers who broke records at the 2008 summer Olympics wore the Speedo Fastskin LZR Racer suit.
In this sports science fair project, you will experiment with drag by swimming with shorts and a T-shirt on, then swimming with a swimsuit on to discover how each affects swim times. Remember to swim as fast as you can. To help improve your swim times, try picturing a shark swimming behind you!
Terms and Concepts
- Can you find other examples of biomimetics?
- What is drag? What are the different kinds of drag?
- How do engineers test for drag?
- What properties of Speedo's Fastskin LZR Racer make swimmers go so fast in it?
- Benson, T. (2008, July 11). What is Drag?. Retrieved December 19, 2008.
This National Geographic article is a good synopsis on biomimetics.
- Mueller, T. (2008, April). Biomimetics: Design by Nature. Retrieved December 19, 2008.
This article discusses Speedo's Fastskin LZR Racer suit:
- Luebbers, M. (n.d.). Speedo Fastskin LZR Racer—The Fastest Swim Suit in the World for 2008!. Retrieved December 19, 2008.
Materials and Equipment
- Swimming pool where you can swim 25 m without any barriers or interruptions
- Measuring tape
- Swimsuit, close-fitting
- Shorts that can get wet
- T-shirt that can get wet
- Lab notebook
- Go to your local swim club or pool and speak to the supervisor. Let him or her know about your science fair project and ask when the best time would be to conduct your tests. You should conduct your tests at a time when the pool is not crowded.
- Ask the supervisor how long the pool is. Record this information in your lab notebook. You should swim at least 25 m to get good measurable times. Use the measuring tape to confirm the length. Be sure to take all your materials with you when you're ready to swim.
- Test your speed with your swimsuit on first. Perform some warm-up exercises before starting the swim.
Now start your swim test. Have your volunteer time how long it takes you to swim 25 m. Have your volunteer record the data in your lab notebook in a data table like the one shown below.
Clothing Swim Time Speed Swimsuit Trial 1 Trial 2 Trial 3 Average speed: Street clothing Trial 1 Trial 2 Trial 3 Average speed:
- Repeat step 4 two more times. Note: Be sure you rest at least 10 minutes between trials!
- Now change out of the swimsuit into the shorts and T-shirt. Repeat steps 4–5. Remind your volunteer to record all data in your lab notebook.
Now calculate the speed of your swims by dividing the distance you swam by how long it took to swim the distance. This is shown in Equation 1.
Speed = Distance Swam
Time to Swim Distance
Plot the data on a scatter plot. Label the x-axis Clothing and the y-axis Speed. Do you see a difference in the speeds? Describe how the water interacted with your street clothes. Describe how drag affected your swim times and speeds. If there was a change in speed, can you calculate the percentage change in speed, shown in Equation 2, below?
Percentage Change = (Average speed with swimsuit - Average speed with street clothing)
Average speed with swimsuit
Ask an Expert
- Does the swim time improve if you try to mimic a fish as much as possible? Wear flippers and swim gloves and redo the project.
- Experiment with drag and body position. For the first body position, kick with your head down and arms stretched above your head, palms together. How long does it take to swim 25 m? For the second body position, swim holding your arms level with your shoulders. Is there a difference in swim time between the two body positions?
- Does drag affect how easily you tire? Swim 50 m and calculate the percent change in speed between swimming with a swimsuit and swimming with street clothes. How does this compare with the percentage change in speed when swimming 25 m?
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