Fluid Mechanics - Highest Possible Water Can go in a Straw

In summary, the conversation is about trying to figure out the highest possible height that water can be sucked up into a straw on Earth, with unlimited water. The method discussed involves creating a vacuum by sucking, which allows the water to rise up due to atmospheric pressure and the force it creates. The highest height would be when this force equals the weight of the water. However, the equations needed to solve this problem are unknown. The conversation also mentions a similar question involving a mercury barometer in free fall.
  • #1
nymetfan21
2
0
I need to figure out the highest possible height that water can be sucked up into a straw on Earth. You have unlimited water.

So far I've figured out that when you suck, you create a vacuum that allows the water to rise up due to the atmospheric pressure and the force is creates pushing down on the rest of the water, which forces to water up the tube. I also figure that the highest height will be when the force the air pressure creates = weight of the water.

I have been unable to figure out the equations to solve this problem to acutally get the height.

Thanks a lot for your help!
 
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  • #2
the pressure causes a Force = P times Area (cross-section A of tube)
the Volume of water in the tube = Area times height.

How do you get a weight from a Volume?

This is NOT advanced Physics ...
you should post questions like these in the INTRODUCTORY physics Area.
 
  • #3
I believe its something like 32 feet.
 
  • #4
Can this be another form of the same question ?
a mercury barometer is under free fall . what would be the height of mercury column in the barometer ?
 
  • #5
lightgrav-

Your method would work if I knew the cross-sectional area. We arent given the cross-sectional area. All we are given is how high can the straw be. We have no other information.
 
  • #6
All you need is \rho g H=P_{atmospheric}.
 

1. How does the diameter of a straw affect the maximum height water can reach?

The diameter of a straw does not affect the maximum height water can reach. The height that water can reach is determined by the balance between gravity and air pressure, which is independent of the straw's diameter.

2. What is the role of surface tension in determining the maximum height water can reach in a straw?

Surface tension plays a crucial role in determining the maximum height water can reach in a straw. It is the cohesive force between water molecules that allows them to stick together and form a curved surface at the top of the straw, which helps to counteract gravity and allows water to rise higher in the straw.

3. Does the type of liquid affect the maximum height water can reach in a straw?

Yes, the type of liquid does affect the maximum height water can reach in a straw. Different liquids have different surface tensions, which can impact the balance between gravity and air pressure and therefore affect the maximum height water can reach in a straw.

4. How does the length of a straw affect the maximum height water can reach?

The length of a straw does not have a significant impact on the maximum height water can reach. As long as the straw is long enough to reach the surface of the water, the height that water can reach will be determined by the balance between gravity and air pressure.

5. Can the maximum height water can reach in a straw be affected by external factors?

Yes, external factors such as temperature and altitude can affect the maximum height water can reach in a straw. Temperature affects surface tension, and higher altitudes have lower air pressure, which can both impact the balance between gravity and air pressure and therefore affect the maximum height water can reach.

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