Sir Isaac Newton was quite the guy, devising the theory of gravity and specifying the three laws of motion. Forces affect everyone and everything, but no one had defined them until Newton. One of the factors that can affect objects in motion is friction. It is easy to understand how friction between a door and its hinge can make the door more difficult to open. It is more difficult to understand how air creates friction, called drag, and slows down everything from butterflies, to people, to airplanes. Gravity is not just an Earth phenomenon. It is the force that holds stars in their galaxies and planets in orbit around stars. We have learned to use gravity and the forces of motion to keep satellites aloft and airplanes in the air. To do the latter, we took a lesson from the birds. The shape of an airplane wing mimics that of a bird’s wing. It is the shape of an airfoil, and the way air moves across it causes lift. Nowhere can you be more keenly aware of gravity and motion than at an amusement park. There, gravity and centrifugal force can make for a wild ride.
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