The solar-car workshop at Boston's Museum of Science, three groups of parents and children are trying out model automobiles they have built. Suddenly everyone rushes back to a workbench to change wheels, adjust the tension on a rubber-band pulley that connects an electric motor to the drive axle, and make other alterations. Meanwhile, another team is attempting to get its refined model to run a test race course in 12 seconds. When it comes close-12.8 seconds-the kids cheer. And in another corner, after 35 minutes of nonstop work to correct a model whose wheels at first spun only when the car was held up in the air, an 11-year-old boy looks around and finds someone he knows. "Come look!" he cries.

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