Bernoulli's principle states that the pressure exerted by a moving stream
of fluid is less than the pressure of the surrojnding fluid.
Example: Blowing above a piece of tissue paper causes it to rise. The greater pressure underneath the paper causes it to rise.
Objects, such as airplane wings, can be designed so that their shapes caue air
to move at different speeds above and below them.
air moves at a greater speed above the object, pressure pushes the object upward.
But if the air moves at a greater speed below the object, pressure pushes it downward.