Heat & Mass Transfer

• Gear Axis Orientations in Mechanical Power Transmission:
• Intersecting Shaft Axes: Exclusively connected using bevel gears (straight bevel, spiral bevel, zerol bevel gears).
• Non-Intersecting Gears:
• Spur gears: Connect parallel shaft axes.
• Rack and pinion: Converts rotational motion into linear motion.
• Helical gears: Primarily connect parallel shaft axes (or crossed skew axes at right angles in crossed-helical gears).
• Conclusion: Gears not used for intersecting axes are (A), (C) and (D) only (Option 4).

Correct option: (4) (A), (C) and (D) only.

• 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).

Evaluating the Assertion and Reason concerning Waste disposal of food processing plants:

The correct answer is Option 1: Both (A) and (R) are correct and (R) is the correct explanation of (A)..