Which Way
Will They Go?

Use string to hang two apples or balloons at the same height and about one inch apart. Blow through the space between them. What happens?

Answer:
We might expect the apples to move apart, but they move toward each other instead. A current of air has less “push,” or air pressure, along its sides than still air has. When air flows between the apples, the air pressure on the outer sides of the apples pushes inward harder than the moving air pushes outward. So air pushes the apples toward each other.