Question: If the airstream from a hair dryer is directed over a table-tennis ball, the ball can be levitated. Explain.
Partial vacuum will lift up the ball.
The sum of the pressure, kinetic energy per unit volume, and gravitational potential energy per unit volume has the same value at all points along a streamline for an ideal fluid. This result is summarized in Bernoulli’s equation:
P = Pressure of fluid
V = Volume of fluid
Density of fluid
h = Height of fluid in pipe
If the stream of air directed over the table tennis ball has very high velocity, it will create a low pressure over the table tennis ball, resulting in partial vacuum that will lift up the ball. This situation is based upon the application of Bernoulli’s principle.
If you release a ball while inside a freely falling elevator, the ball remains in front of you rather than falling to the floor because the ball, the elevator, and you all experience the same downward gravitational acceleration. What happens if you repeat this experiment with a helium-filled balloon?
Question: Two thin-walled drinking glasses having equal base areas but different shapes, with very different cross sectional areas above the base, are filled to the same level with water. According to the expression , the pressure is the same at the bottom of both glasses. In view of this equality, why does one weigh more than the other?
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