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Grade 12th passMechanics

A liquid flows through a horizontal pipe whose inner radius is 5.35 cm. The pipe bends upward through a height of 9.5 m where it widens and joins another horizontal pipe of inner radius 6.8 cm. What must the volume flux be if the pressure in the two horizontal pipes is the same

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5 Years agoGrade 12th pass
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ApprovedApproved Tutor Answer1 Year ago

To determine the volume flux of the liquid flowing through the pipes, we can apply the principles of fluid dynamics, particularly the continuity equation and Bernoulli's equation. Since the pressure in the two horizontal pipes is the same, we can simplify our calculations significantly.

Understanding the Problem

We have two sections of a pipe: the first section has an inner radius of 5.35 cm, and the second section has an inner radius of 6.8 cm. The liquid flows from the first section to the second, with a vertical rise of 9.5 m in between. However, since the pressure in both horizontal sections is equal, we can focus on the relationship between the cross-sectional areas and the velocities of the liquid in each section.

Key Concepts

  • Continuity Equation: This principle states that the mass flow rate must remain constant in a closed system. For incompressible fluids, this can be expressed as: A_1 v_1 = A_2 v_2, where A is the cross-sectional area and v is the fluid velocity.
  • Cross-Sectional Area: The area of a circle is calculated using the formula: A = πr², where r is the radius.

Calculating Areas

First, we need to calculate the cross-sectional areas of both pipes:

  • For the first pipe (radius = 5.35 cm): A_1 = π(0.0535 m)² ≈ 0.00899 m²
  • For the second pipe (radius = 6.8 cm): A_2 = π(0.068 m)² ≈ 0.01453 m²

Applying the Continuity Equation

Using the continuity equation, we can relate the velocities in both sections:

A_1 v_1 = A_2 v_2

Rearranging gives us:

v_2 = (A_1 / A_2) v_1

Volume Flux Calculation

The volume flux (Q) is defined as the product of the cross-sectional area and the velocity:

Q = A v

For both sections, we have:

  • Q_1 = A_1 v_1
  • Q_2 = A_2 v_2

Since the volume flux must be the same in both sections (Q_1 = Q_2), we can set them equal:

A_1 v_1 = A_2 v_2

Substituting for v_2 gives:

A_1 v_1 = A_2 (A_1 / A_2) v_1

This confirms that the volume flux is constant, and we can express it in terms of either section. Let's calculate the volume flux using the first pipe:

Q = A_1 v_1

Final Calculation

To find the volume flux, we need the velocity of the liquid in the first pipe. However, since we don't have that value directly, we can express the volume flux in terms of the areas:

Q = A_1 v_1 = A_2 v_2

Assuming we know either velocity or can measure it, we can calculate the volume flux. If we assume a hypothetical velocity for the first pipe, say 2 m/s, we can find:

Q = 0.00899 m² * 2 m/s ≈ 0.01798 m³/s

Thus, the volume flux through both pipes would be approximately 0.01798 m³/s, assuming the velocity of the liquid in the first pipe is 2 m/s. You can adjust the velocity based on actual measurements or conditions to find the specific volume flux for your scenario.