In a hydrometer analysis, for estimating particle size distribution of fine-grained soil, it is assumed that
- AAll particles are of same specific gravity
- BTerminal velocity is attained immediately after starting the test
- CThe test is applicable for colloid sized particles
- DBoth (A) and (B)Correct
Solution
Concept
Assumptions of hydrometer analysis
Step-by-step solution
1. All particles are assumed to have the same specific gravity. 2. Particles are assumed to reach terminal velocity immediately. 3. Both (A) and (B) are assumptions.
Explanation
Stokes' law is applied with these assumptions.
Why the other options are wrong
The test applies to particles larger than about 0.2 μm, not truly colloidal ones.
Shortcut
Stokes assumptions.
Correct answer: D) Both (A) and (B)