It doesn't involve flying or blowing a roof off a house, but it will be just as impressive-in fact it will almost be magical! You are going to perform one of them in this activity. There are many more demonstrations of Bernoulli's principle in the real world. This higher-pressure air pushes up on the wing and thus creates an upward lifting force (similar to the roof example above). This creates a pressure difference in which the pressure on the top of the wing is lower than on the bottom. Airplane wings are designed to let the air flowing over the top move faster than the air flowing underneath. As a result the ball stays afloat on top of the fan.īernoulli's principle can also explain how lift is generated under an airplane wing. When the ball starts to fall off the column of air above the fan, the surrounding higher-pressure air pushes the ball back into the area of lower pressure above the fan. The fast-moving air, which carries the ball into the air, is at a lower pressure than the air surrounding the ball. Why does the ball not fly off the fan? It is because of Bernoulli's principle. A simple demonstration of Bernoulli's principle requires floating a ping pong ball in a moving stream of air, for example on top of a fan or hairdryer pointed straight up. It is not only true for fluids but also for air because gases-just like fluids-are able to flow and take on different shapes. His discovery became known as the Bernoulli principle. He realized that fast-moving fluids produce less pressure and slow-moving fluids produce greater pressure. When experimenting with fluids flowing through an hourglass-shaped tube, he made a discovery. The roof experiences lift, similar to an airplane wing, and flies away! In this activity you will put Bernoulli's principle to work-but do not worry, your roof will be safe!ĭaniel Bernoulli was a Swiss scientist who in the 18th century studied how fluids behave when they are in motion. Eventually the pressure difference becomes large enough that the air inside the house starts pushing on the roof. This creates a pressure difference between the air outside and the air inside the house. In a hurricane the fast flow of air above the roof's shape generates a low-pressure area. Have you ever seen pictures or videos of a roof being blown off a house during a hurricane or tornado? You might be surprised to hear that the roof is actually not blown off by the strong winds but instead by the air inside the house! This can be explained by Bernoulli's principle, which states that fast-moving fluids or air, such as strong winds, have lower pressure than slow-moving air.
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