How Does Fluid Dynamics Explain Pressure Differences and Density Calculations?

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SUMMARY

The discussion focuses on fluid dynamics, specifically addressing pressure differences and density calculations in various scenarios. A participant calculated that the air pressure at the floor of a 15.0m tall building is 0.17% greater than at the ceiling. Another participant applied the hydrostatic pressure formula, P=Po+(density)(g)(h), to determine the pressure in a U-shaped tube containing mercury and water, but encountered issues with the results. Additionally, a question regarding the density of a partially submerged cylindrical rod highlighted the need for radius information to calculate displaced volume.

PREREQUISITES
  • Understanding of hydrostatic pressure principles
  • Familiarity with the formula P=Po+(density)(g)(h)
  • Basic knowledge of density and buoyancy concepts
  • Experience with fluid mechanics applications
NEXT STEPS
  • Study hydrostatic pressure calculations in different fluid scenarios
  • Learn about buoyancy and Archimedes' principle in fluid dynamics
  • Explore the implications of density variations in fluid mechanics
  • Investigate common errors in web-based physics grading systems
USEFUL FOR

Students and educators in physics, particularly those focusing on fluid dynamics, pressure calculations, and density assessments. This discussion is also beneficial for anyone using web-based grading systems for physics coursework.

laminar
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A building is 15.0m tall. By what percent is the air pressure at the floor greater than the air pressure at the ceiling? The floor is at sea level. -- I don't understand what this percentage relates to, and I got 0.17% greater.

A U-shaped tube, open to the air on both ends, contains mercury. Water is poured into the left arm until the water column is 12.9 cm deep. How far upward from its initial position does the mercury in the right arm rise? -- The pressure at one point is equal to the pressure at any other point if they are at the same depth.

So, P=Po+(density)(g)(h)

P=101300+(1000)(9.8)(0.129)

P=102564.2Pa

Then make this equal to the pressure in the arm with the mercury in it:

102564.2=101300+(13600)(9.8)(d)

I got d=0.95cm, and the computer says it isn't right. I hate this MasteringPhysics crap. Am I doing something wrong here?

A long cylindrical rod is partially submerged in water. 1.60m of the 6.80m long rod is out of the water. What is its density? -- Don't we have to know the radius, so we can get the area, so we can find the volume displaced by the submerged portion?
 
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This is why I hate web-based grading systems. You never know if you're way off or if it is an error of one or two.
 

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