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imagine you're at a party, and someone pulls out a pint glass, a sieve, and a plate. sounds like the start of a magic trick, right? well, it is! but this trick is all about fluids, surface tension, and the fascinating world of fluid dynamics. let's dive into the science behind this magic act and explore how it's connected to pitot tubes, badger meters, and other measuring devices.
the magic of surface tension
in the experiment, tom crawford, a mathematician and fluid dynamics expert, demonstrates the power of surface tension using a sieve with small holes. when he pours water into the sieve, it falls through, as expected. but when he places the sieve on top of a pint glass, covers it with a plate, and turns it over, something magical happens. the water stays in the glass, even when he removes the plate! how is this possible?
the answer lies in surface tension. surface tension is the force that holds the surface of a liquid together, acting like a thin, elastic skin. in this case, the surface tension of the water is strong enough to hold it in the glass, preventing it from falling through the sieve's tiny holes. this is the same force that allows some insects to walk on water and creates beautiful droplets on leaves after a rainstorm.
the sieve and the colander
now, let's try the experiment with a colander, which has much larger holes. when tom pours water into the colander and performs the same trick, the water falls out. why? because the surface tension of the water is not strong enough to hold it in place when the holes are too large. this demonstrates the importance of hole size in determining whether surface tension can keep the water in the container.
the pitot tube and badger meter
while the experiment with the sieve and colander is a fun demonstration of surface tension, it's also connected to the world of fluid dynamics and measuring devices. for example, a pitot tube is a device used to measure fluid flow velocity. by understanding the principles of fluid dynamics, including surface tension, scientists and engineers can design more accurate and efficient pitot tubes and other measuring devices, such as badger meters, which measure the flow rate of liquids.
the flow free equation and mass flow rate equation
to further explore the connection between fluid dynamics and measuring devices, let's take a look at two important equations: the flow free equation and the mass flow rate equation. the flow free equation, also known as the continuity equation, describes how the flow of a fluid changes as it moves through a system. the mass flow rate equation, on the other hand, calculates the amount of mass that flows through a given area per unit time. both equations are crucial for understanding fluid dynamics and designing accurate measuring devices.
the pressure equation
another important equation in fluid dynamics is the pressure equation. this equation helps us understand how pressure changes as a fluid moves through a system. by knowing the pressure at different points in a system, scientists and engineers can design more efficient and effective measuring devices, such as pitot tubes and badger meters.
wrapping up
so, the next time you see a pint glass, sieve, or colander, remember the magic of surface tension and the fascinating world of fluid dynamics. and don't forget to think about how this magic is connected to pitot tubes, badger meters, and other measuring devices. who knew that a simple experiment could lead to such a deep understanding of the science behind fluids?
for more information on fluid dynamics and measuring devices, check out these resources:
- trapped water and tiny holes - numberphile - tom crawford shows why water doesn't fall through a sieve with small enough holes.
- tom crawford's website - links to his work and other outreach activities.
- more tom videos on numberphile - watch more of tom's videos on fluid dynamics and mathematics.
- numberphile - a website dedicated to exploring the wonders of mathematics and science.
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