The design of a wing's cross-section, or airfoil, will affect the amount of lift and drag it produces. While airfoils come in different shapes for different purposes, they all use the same physics: altering the flow of air to create forces that push the airfoil upward or downward. The wings of a fighter jet, for instance, are extremely thin, allowing the plane to cut through the air efficiently. However, they produce relatively little lift, so the plane has to move very fast to stay in the air. In contrast, the spinning blades above a helicopter—long, thin wings that produce lift as they rotate—allow a helicopter to hover in place, but not fly very fast.

Most discussions of lift focus on airplanes: how they get up into the air and stay there. But the same physical principles apply to other familiar items: boat propellers, wind turbines, even bird feathers. One interesting place to examine lift is in the design of race cars. Unlike airplanes, which have wings that help them lift up, race cars have inverted wings that help them cling to the track during high-speed races.

By the middle of the 20th century, engineers understood airfoils so well that they could design wings precisely suited to the needs of different planes, from fighter jets to crop dusters. Race car designers, however, didn't make the connection between planes and cars right away. At first, they focused mostly on reducing drag—streamlining cars so they would meet less air resistance and move faster.

But fast, streamlined race cars have a problem, especially around turns: If they are going too fast, the car will generate lift and fly off the track. Race car designers began to borrow from airplane designers and put wings on their cars, only their wings were upside down. On most planes, the wings, viewed in profile, curve out on the top in smooth, rounded humps. The inverted wings on race cars are just the opposite: they are concave scoops that look more like shovels than wings. Most race cars today have at least two inverted wings: a front wing close to the ground and a rear wing in the air. Rather than lifting the car up, these create downward pressure—or "negative lift"—to press the car down toward the ground. This downward pressure creates more traction between the tires and the track, so the driver can turn, accelerate, and stop the car more quickly.

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