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Hello, my name is Jenna. I am an 8th grade student at La Colina J.H. I am currently working on my science fair project. My Science fair question is:

How does a wetsuit affect drag?

My procedures are:
1.Wear a competition swimsuit.
2. Swim in 25m pool
3. Swim 100m.
4. Measure and document time of 100m swim.
5. Rest 2 minutes.
6. Repeat steps 1-5 nine times.
7. Average the times of all 100m swim sets.
8. After a week of rest, wear a triathlon swimming wetsuit of 3mm thickness neoprene with no arms.
9. Repeat steps 2-7 wearing wetsuit.
My hypothesis is: If the wetsuit does create drag then I think the competitive swimsuit will provide better speed and time then the wetsuit. IF you have the time I would really appreciate answers to these questions.
a. Do my procedures sound like they would work for my experiment?
b. Is there anything I could do to make my experiment better?
c. Would it be better to do five trials of the competition suit and then five trials of the wetsuit on one day then do the same thing a week later?
d. Is there any vital information about drag I should know before conducting my experiment?
e. What is the best way to measure drag?

Question Date: 2012-11-08
Answer 1:

I like your experiment. I like the plan in (c) better; but I think you should do one day with competition wet suit first, and the other day with wet suit first. Then you have a better control in the experiment, because I'm guessing you swim faster in the earlier swims? Or, if you swim faster in the later swims, you have each wet suit 'doing' later swims. And, if you're just more energetic on one day than the other, you'll have swim times in each wet suit on each day.

Google Scholar is a good place to learn about things such as how to measure drag. It's at scholar.google.com

Here's one result, for my search of "wet suit drag":
The effect of a triathlon wet suit on drag was studied in 12 subjects (eight male, four female) swimming at different velocities (1.10, 1.25 and 1.50 m.s-1). The active drag force was directly measured during front crawl swimming using a system of underwater push off pads instrumented with a force transducer (M.A.D. system: 6). Measurements were made when swimming over the system with and without a wet suit. A 14% reduction in drag (from 48.7 to 41.8 Newtons) is found at a swimming velocity of 1.25 m.s-1, which is a typical swimming speed for triathlon distances. At 1.50 m.s-1 a reduction in drag of 12% was observed, which suggests that the wearing of such a suit might be beneficial in conventional swimming events. The reduction in drag can explain the higher swimming velocities observed in triathletes using a wet suit. The effect of the reduction is probably largely due to an increased buoyancy inducing less frontal resistance. However, since the effect of the suit on the lighter female swimmers was not different from the effect on the heavier male swimmers, a reduction in friction drag and drag coefficient may also be significant.

This is the article:
Toussaint HM, Bruinink L, Coster R, De Looze M, Van Rossem B, Van Veenen R, De Groot G Department of Exercise Physiology and Health, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands. Medicine and Science in Sports and Exercise [1989, 21(3):325-328]

Keep asking questions!
Best wishes,

Answer 2:

Do my procedures sound like they would work for my experiment?
I'm not sure that you will be able to answer your original, scientific question of "how". The procedures sound like they answer the question of "Which suit provides a better speed swimming in a pool?" I don't think you will be able to directly look at the drag, but rather you are looking at how fast a suit can make you.

Is there anything I could do to make my experiment better?
I'm not sure what you mean in either of the suits that you have here - do they have legs to the knee? to the ankle? sleeves? back cut outs? So if you have a "regular" competition swim suit (a one-piece that is similar to what people would think of as a swim suit), I would then also look at something that adds to the knee, and a different one that adds to the ankle, IF you can borrow one. If not, I think this will still work, and show the differences.

I would also repeat the whole thing another time - so once more with the competition suit, and once more with the triathlon suit.

Also, it's the same person completing all of these swims right? You don't want to have 2 different people completing these swims.

Would it be better to do five trials of the competition suit and then five trials of the wetsuit on one day then do the same thing a week later?

I think you can cut down on the number of times you need to time at each trial - but you don't want to be too worn down when you switch suits. If you do them all in one day, make sure to switch which one you use the second time. For example if the first swims are with a competition swimsuit on day 1, Day 2 should have the triathalon wet suit as the first swims. If you have the time, and conduct your experiment this way, I'd add a few more days of timing.

Is there any vital information about drag I should know before conducting my experiment?

What is the best way to measure drag?
See comment in (a)

Also, you can e-mail if you have more questions/ want to bounce ideas around.

Answer 3:

Nice experiment! I have the following suggestions:

1. Have a partner besides yourself whom you also do the experiment on, but have your partner wear the wet suit first (while you're wearing the swimsuit), and then a week later have her wear the swimsuit while you're wearing the wet suit. Also make sure that if either she or you swim in the week between your measurements, make sure that the two of you swim together. The reason is because if you're swimming regularly in-between trials, then you might be in better physical shape in the second trial than in the first, and thus perform better. If, instead, you don't swim in-between trials, then you might have lost some of your physical fitness, and this could affect your results. If you swim with a partner who is wearing whichever outfit you're not, and both of you swim better (or worse) the second week than on the first, then you can attribute that to being in better/worse shape than you were in the first trial and not to the outfit you were wearing while taking the measurement.

2. You could do five and five for each day, but also keep in mind that you're going to be tiring yourself every time you swim on a given day. This will cause you to not swim as fast, which you don't want to confuse your results.

3. I'd measure it as how fast you can get to the other side of the pool.

4. If you're even mildly sick one day, don't swim. Wait. Postpone your experiment if you have to. It will hurt your performance, and therefore screw with your data.

Good luck!

Answer 4:

I really like your research question and experiment. Your experimental design is well set up and you should get some interesting results. Keep in mind that there are different forms of drag. There is friction drag. Friction drag is the drag that results from the interaction between the swimmer´s body and the water molecules and serves to slow down the swimmer. Then there is pressure drag. Pressure drag occurs because the swimmer is moving through the water and there is a difference in the amount of pressure in front and back of the body. This difference in pressure causes turbulence around the swimmers body and can slow down the swimmer. Among other factors, this kind of drag will be a function of how the swimmer's body is positioned in the water. Last of all there will be wave drag, which occurs when the swimmer or any object moves through the surface of a liquid.

So what does this mean for your experiment? It means that you should observe and think about how the competivie swimsuit and wetsuit affects all forms of drag. Obviously the material on the swimmers body will be different so the skin friction will be different but does the wet suit cause the swimmer´s body to position differently in the water as well? For example, will your legs be dangling deeper in one of the suits? Will your body be sticking out into the air more in one of the two suits? If you can estimate these variables or at least observe them then your results will be much more informative in understanding the effect of the suits on drag.

Also don´t forget to make observations about how the competitive suit versus wetsuit affect other factors than drag. For example, does one of the two suits affect swimming mechanics in a different manner? Are you able to move your arms and legs in the same way in the two experimental trials? Even if you can´t measure these other variables you should obverse them and mention them in your results and discussion. If you have time you could also test how fast you swim in just a regular swimsuit.

Feel free to contact me if you have more questions.

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