Water manometer to measure change in pressure

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SUMMARY

The discussion focuses on calculating the change in pressure of a gas using a water manometer in a specific heat experiment. The atmospheric pressure is given as 1.4 x 105 Pa. The user initially calculated the gauge pressure using the formula P = ρgd, resulting in an incorrect value of 392.4 kPa instead of the correct 392.1 Pa. The error was identified as a miscalculation in unit conversion, emphasizing the importance of careful dimensional analysis in physics problems.

PREREQUISITES
  • Understanding of gauge pressure and absolute pressure concepts
  • Familiarity with the formula P = ρgd for pressure calculations
  • Knowledge of unit conversions, particularly between Pa and kPa
  • Basic principles of thermodynamics related to specific heat
NEXT STEPS
  • Review the principles of gauge pressure and its applications in fluid mechanics
  • Study unit conversion techniques, especially between different pressure units
  • Explore the relationship between specific heat and gas laws in thermodynamics
  • Learn about the practical applications of manometers in experimental physics
USEFUL FOR

Students in physics or engineering courses, particularly those involved in laboratory experiments related to thermodynamics and fluid mechanics.

BlueSkyy
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Homework Statement



An experiment to determine the specific heat of a gas makes use of a water manometer attached to a flask (the figure below ). Initially the two columns of water are even. Atmospheric pressure is 1.4 x 10^5 Pa. After heating the gas, the water levels change to those shown. Find the change in pressure of the gas in Pa.

https://chip.physics.purdue.edu/protected/GiambattistaMimg/chapter-09/fig-035.gif

Homework Equations



P = pgd (gauge pressure)
Pgauge = Pabs - Patm

The Attempt at a Solution



well, i took (1000 kg/m3)x(9.81m/s2)x(.04m) and got 392.4 kPa...that's 392400 Pa, right?
but it's not correct...where did i go wrong? i know that it is displaced .02m up and .02m down for a total of .04m, and the density of water is 1000kg/m3 (for this problem)

any help would be appreciated!
 
Physics news on Phys.org
1000x9.81x.04 = 392.1Pa., not kPa
 

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