Question

The principle of sedimentation of soil particles in soil texture analysis is based on

• A. Stokes’ law
• B. Bernoulli’s principle
• C. Voncoffs’ principle
• D. Liebig’s law of the minimum

Hint:

Stokes' Law tells us why clay makes pond water cloudy for days—it's so small that its settling velocity is near zero. For pond construction, we want soil with high clay content for its water-holding capacity.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question refers to the scientific law that governs the rate at which different-sized soil particles (sand, silt, clay) settle in a liquid, which is the basis for determining soil texture in pond construction and management.
Key Formula or Approach:
Stokes' Law describes the terminal settling velocity ($v$) of a small spherical particle in a viscous fluid: \[ v = \frac{2}{9} \frac{(\rho_p - \rho_f)}{\eta} g r^2 \] Where: - $r$ is the radius of the particle. - $g$ is the acceleration due to gravity. - $\rho_p$ and $\rho_f$ are the densities of the particle and fluid. - $\eta$ is the dynamic viscosity of the fluid.

Step 2: Detailed Explanation:

• Application in Soil Science: In soil texture analysis (like the Hydrometer method or Pipette method), soil is dispersed in water. According to Stokes' law, the velocity of settling is proportional to the square of the radius of the particle.
- Sand particles (largest) settle very quickly.
- Silt particles settle moderately.
- Clay particles (smallest) settle very slowly and may remain in suspension for a long time.

• Liebig’s Law (Option D): States that growth is controlled not by total resources, but by the scarcest resource (limiting factor).

• Bernoulli’s Principle (Option B): Relates the pressure and velocity of a moving fluid (used in hydraulics and aerodynamics).

Step 3: Final Answer:
Soil particle sedimentation is based on Stokes’ law.