Nina, Rosario, and Mike must build a homemade go-kart out of junk that can coast downhill, steer, and brake. An expert soap box derby car builder is on hand to teach them about the importance of gravity, friction, and drag in go-kart racing. The kids design and build their own go-kart, make adjustments, and finally compete in a race against a real Soap Box Derby car. Meanwhile, Bridget meets up with a Chinese culture expert to learn the traditions behind the Chinese Dragon Boat Festival (held every year to bring luck and prosperity). In addition to boat racing, Bridget learns many of the cultural traditions behind the festival, including how to make zongzi.