By Clara Slight

I have swum all my life. Since we
learned recently about drag force, I decided to calculate the drag force that
is encountered while swimming. I decided to calculate this for two different
aspects: for your hand while swimming freestyle and then for your entire body.
When you take a stroke while swimming, your hand is moving faster than your
entire body. I made some estimates, and used a velocity of 3 m/s, a
cross-sectional area of .10 m, a viscosity of water of 8.9*10

^{-4}, and a coefficient of drag of a half sphere or .42 (http://swimright23.webs.com/dragandresistance.htm). The drag force that a hand encounters while swimming freestyle is F_{d}= 1/2pC_{d}v^{2}A = ½(8.9*10^{-4})(.42)(3^{2})(.1) = 1.68*10^{-4 }N. For the entire body, the calculations change. I also made some estimates here, using a velocity of 1 m/s, a cross-sectional area of .4 m, the same viscosity of water, a coefficient of drag of a streamlined half body or .09. The drag force that a body encounters while swimming freestyle is F_{d}= 1/2pC_{d}v^{2}A = ½(8.9*10^{-4})(.09)(1^{2})(.4) = 1.60*10^{-5}. It is interesting to note that when a swimmer is completely submerged, the drag coefficient decreases to .04 and the subsequent drag force is less. The calculated value is F_{d}= 1/2pC_{d}v^{2}A = ½(8.9*10^{-4})(.04)(1^{2})(.4) = 7.12*10^{-6}. It is also interesting to observe that as the velocity increases, so does the drag force, which makes sense.
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