Math Problem Statement

A manometer (pressure-measuring device) uses mercury (sg=13.6) as the fluid. A reading of 5 inches on the manometer is equivalent to how many millimeters of kerosene (sg=0.82)? (2106.34146 mm

Solution

We can solve this problem by applying the principle of hydrostatic pressure, which states that the pressure exerted by a fluid column is proportional to the height of the column and the specific gravity of the fluid.

Here are the steps:

Step 1: Pressure relation

The pressure exerted by a column of fluid is given by: P=hSGρwatergP = h \cdot \text{SG} \cdot \rho_{\text{water}} \cdot g where:

  • PP is the pressure,
  • hh is the height of the fluid column,
  • SG\text{SG} is the specific gravity of the fluid,
  • ρwater\rho_{\text{water}} is the density of water (used as a reference density),
  • gg is the acceleration due to gravity.

Since pressure must be equal in both cases (for mercury and kerosene):

hHgSGHg=hkeroseneSGkeroseneh_{\text{Hg}} \cdot \text{SG}_{\text{Hg}} = h_{\text{kerosene}} \cdot \text{SG}_{\text{kerosene}}

Step 2: Convert height of mercury to kerosene

We are given:

  • hHg=5 inchesh_{\text{Hg}} = 5 \text{ inches},
  • SGHg=13.6\text{SG}_{\text{Hg}} = 13.6 (mercury),
  • SGkerosene=0.82\text{SG}_{\text{kerosene}} = 0.82.

First, convert 5 inches to millimeters: 5 inches=5×25.4=127 mm5 \text{ inches} = 5 \times 25.4 = 127 \text{ mm}

Now use the pressure relation to find hkeroseneh_{\text{kerosene}}: 12713.6=hkerosene0.82127 \cdot 13.6 = h_{\text{kerosene}} \cdot 0.82

Solve for hkeroseneh_{\text{kerosene}}: hkerosene=12713.60.82=2106.34 mmh_{\text{kerosene}} = \frac{127 \cdot 13.6}{0.82} = 2106.34 \text{ mm}

Final Answer:

The equivalent height of kerosene is approximately 2106.34 mm.

Do you want further details or explanations on any part of the solution?

Here are 5 related questions to expand on this concept:

  1. What is the relationship between pressure and fluid column height in manometry?
  2. How does the specific gravity of a fluid affect the height of the column?
  3. Can you convert the height of other fluids using the same method?
  4. How would the height change if a fluid with a higher specific gravity than mercury was used?
  5. Why is it important to use a reference fluid like water for calculating specific gravity?

Tip: Always ensure that units are consistent when applying pressure or height calculations in hydrostatics.

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Math Problem Analysis

Mathematical Concepts

Hydrostatics
Specific Gravity
Pressure Equivalence

Formulas

P = h ⋅ SG ⋅ ρ_water ⋅ g
h_Hg ⋅ SG_Hg = h_kerosene ⋅ SG_kerosene

Theorems

Principle of Hydrostatic Pressure

Suitable Grade Level

Grades 10-12