The Physics of Vacuums: Understanding Force and Gravity

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The force associated with a vacuum is primarily atmospheric pressure, which counteracts gravity when a straw is used to lift liquid. When the end of the straw is pinched, the pressure inside decreases, allowing atmospheric pressure to push the liquid upward. However, if the straw is too long, the weight of the fluid column can exceed the atmospheric pressure, causing the liquid to fall. This phenomenon illustrates the balance between gravitational force and atmospheric pressure in fluid dynamics. Understanding these forces is crucial for grasping the physics of vacuums.
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What is the force associated with a vacuum? If I put a straw in a soda and pinch off the end of the straw, then lift it out of the soda, some soda stays. What force counteracts gravity?
 
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It is the atmospheric pressure that pushes the liquid up the straw.Since you reduce the pressure inside the straw the downward force on the liquid is only the force of gravity, the upward force due to pressure remains so the fluid goes up. If you try to do this with a very long straw you would reach a point where the weight of the fluid column is greater than the force due to the atmospheric pressure and the fluid would fall.
prof Walter Lewin did an amazing lecture on this here:
 
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