Soil-Water-Plant Relationships

• Aerodynamic Characteristics of Darrieus Wind Rotor:
• The Darrieus rotor is a vertical-axis wind turbine (VAWT) featuring curved aerofoil blades resembling an eggbeater:
• Low starting torque: Cannot self-start because at low tip-speed ratios, blade angles of attack stall relative to incoming wind.
• Self-starting: False (requires an auxiliary Savonius rotor or motor to start).
• High operating speed: Operates at high tip-speed ratios ($TSR \gt 4$).
• High aerodynamic efficiency: Can attain power coefficients ($C_p$) exceeding 0.35–0.40, approaching horizontal-axis turbines.
• Conclusion: Correct characteristics are (A), (C) and (E) only (Option 3).

Correct option: (3) (A), (C) and (E) only,

• Peak Combustion Pressure in Diesel Combustion Chambers:
• Precombustion Chambers (Indirect Injection - IDI) divide the combustion space into a small prechamber (20–40% volume) and a main chamber above the piston.
• Fuel injected into the prechamber ignites with limited oxygen, forcing rich, partially burned gases through an orifice into the main chamber, where complete burning occurs progressively.
• This two-stage progressive burning cushions the pressure rise and produces the lowest peak cylinder pressure and lowest rate of pressure rise compared to open (direct injection) chambers.
• Conclusion: Peak pressure is lowest for Precombustion chamber (Option 2).

Correct option: (2) Precombustion chamber

• Rotary vs. Sickle Bar Mowers:
• Assertion (A): The power requirement of a rotary mower is much higher than that of a sickle bar mower of the same width. $\implies$ True.
• Rotary mowers cut by high-velocity impact without a ledger plate, operating at blade tip speeds of 70–80 m/s, incurring high aerodynamic windage and impact energy losses (3–5 times more power than sickle bar mowers).
• Reason (R): The knives of rotary mower are hinged to the disc or drum so that they can swing back if they hit a rock or other obstruction; centrifugal force keeps the knives in cutting position during normal operation. $\implies$ True.
• Rotary mower knives are freely pivoted for obstacle safety.
• Relationship: Reason (R) describes a safety mechanism for obstacle evasion, not the physical cause of high power consumption (which stems from aerodynamic drag and high-velocity impact).
• 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).