Can Suction Lift a 20 Meter Water Column Without Exceeding Its Tensile Strength?

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SUMMARY

The discussion focuses on calculating the suction pressure required to support a 20-meter high column of water and whether this pressure exceeds the tensile strength of water, which is 20 MPa. The calculations involve using the formula for pressure, defined as Force divided by Area, and the concept of bulk modulus. The surface area of the column is determined to be 63.62 square units. The discussion also touches on the phenomenon of water rising in a straw due to suction, prompting further exploration of the effects of a perfect vacuum.

PREREQUISITES
  • Understanding of fluid mechanics principles
  • Familiarity with pressure calculations
  • Knowledge of tensile strength and bulk modulus concepts
  • Basic geometry for calculating surface area
NEXT STEPS
  • Research the implications of tensile strength in fluid dynamics
  • Learn about the effects of bulk modulus on liquid behavior
  • Explore practical applications of suction in engineering
  • Investigate the physics behind fluid movement in straws and siphons
USEFUL FOR

Students studying fluid mechanics, engineers working with hydraulic systems, and anyone interested in the physics of suction and pressure in liquids.

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Homework Statement



What suction (or negative pressure) is required to support a column of liquid 20 m high? Does this exceed the tensile strength of water?

Homework Equations



Bulk Modulus = (Change in Pressure/ (Change in Volume/Volume))
Pressure = Force / Area

The Attempt at a Solution



Tensile strength of water = 20 MPa

Pressure = Force / Area

Assume column has a diameter of 1 unit.
The surface area of this column is thus:

Circumference x Height of column + Area of top of column

= 62.83 + 0.79
=63.62 units2


 
Physics news on Phys.org
Do you know why water rises in a straw when you suck on it?
If you do, then assuming that you have an extremely long straw, can you calculate how high the water would rise if you had perfect vacuum (zero pressure) inside the straw?
 

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