Olympic swim star Missy Franklin, 17, is making a big splash at the 2012 London Games. The American swimmer, who entered her first Olympics already a world record holder, earned her first gold medal in the women's 100-meter backstroke event on July 31. She has also won a gold in the 4x200m freestyle relay and a bronze in the 4x100 freestyle relay—and there are more events to come.

How do Franklin and other world-class swimmers achieve such high speeds? Watch the video below to learn how Franklin must use her body and technique to fight against drag forces in the pool. The video is part of the "Science of the Summer Olympic Games: Engineering in Sports" video series from NBC Learn, the educational division of NBC News. Other videos in the series, which were created in a partnership with the National Science Foundation, look at the mechanics of weightlifting, the strength and flexibility of double amputee sprinter Oscar Pistorius and more. Watch more videos at nbclearn.com.