Irrigation Systems

• Balancing of Mower Pitman Drives:
• Assertion (A): The rotating counterweight commonly provided on the flywheel of a mower pitman drive does not give complete balancing. $\implies$ True.
• rotating counterweight generates a centrifugal force in all radial directions ($360^\circ$), whereas the knife reciprocates linearly along a single horizontal axis; balancing the horizontal inertia force introduces an unbalanced vertical force.
• Reason (R): Inertia force of the knife varies as the square of crank speed and as the first power of stroke. $\implies$ True.
• For simple harmonic motion, maximum inertia force is $F_i = m \omega^2 r = m \omega^2 (S/2) \propto N^2 \cdot S$.
• Relationship: Reason (R) defines the magnitude of reciprocating inertia, while Assertion (A) stems from the directional mismatch between rotating counterweights and linear reciprocation.
• Conclusion: Both (A) and (R) are true but (R) is NOT the correct explanation of (A) (Option 2).

Correct option: (2) Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

• ISSS Soil Particle Size Classification:
• According to the International Society of Soil Science (ISSS) standards:
• Coarse sand: $2.0\text{ mm}$ to $0.2\text{ mm}$
• Fine sand: $0.2\text{ mm}$ to $0.02\text{ mm}$ ($0.02 - 0.2\text{ mm}$)
• Silt: $0.02\text{ mm}$ to $0.002\text{ mm}$
• Clay: $\lt 0.002\text{ mm}$
• USDA Comparison: USDA classifies very fine sand as $0.1 - 0.05\text{ mm}$ and silt as $0.05 - 0.002\text{ mm}$.
• Conclusion: Fine sand diameter ranges from 0.02 to 0.2 mm (Option 2).

Correct option: (2) 0.02 to 0.2mm