• 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).

• Operational Characteristics of Screw Conveyors:
• screw conveyor consists of a helical auger revolving inside a stationary U-shaped or cylindrical trough.
• Due to continuous rubbing friction between the material, auger flights, and trough wall:
• Power consumption is relatively high compared to belt conveyors or bucket elevators ($2-3$ times higher power).
• Continuous abrasive contact makes screw flights and bearings more susceptible to wear.
• Conclusion: Require relatively high power and are more susceptible to wear (Option 2).

Correct option: (2) Require relatively high power and are more susceptible to wear