• Cut-Off Diameter of Cyclone Separators:
• Lapple's Cut Diameter Equation ($d_{pc}$):

• Governing Factors:
• Inlet diameter / width ($W$): Determines the radial distance a particle must travel to strike the collector wall.
• Inlet air velocity ($v_i$): Generates the centrifugal vortex acceleration ($v_i^2 / r$).
• Effective number of turns ($N_e$): The number of helical gas revolutions inside the cyclone barrel and cone.
• (D) Pressure drop is a hydraulic consequence of gas flow rather than an independent parameter in the analytical cut-off equation.
• Conclusion: (A), (B) and (C) only (Option 2).

Correct option: (2) (A), (B) and (C) only,

• AutoCAD JOIN Command:
• Function: In Computer-Aided Design (AutoCAD), the JOIN command (J) connects collinear lines, open arcs, elliptical arcs, and splines that share common endpoints into a single continuous polyline object.
• Other Commands:
• Merge: Used in layers or data sets.
• Add: Mathematical insertion.
• Combine: Boolean 3D solid modeling command.
• Conclusion: Join (Option 4).

Correct option: (4) Join

• Velocity Ratio of Belt Drive Transmission:
• Formula:

• Calculation:
• Driving shaft speed ($N_1$) = $60\text{ rpm}$
• Driven shaft speed ($N_2$) = $170\text{ rpm}$

• Conclusion: Velocity ratio is 17/6 (Option 2).

Correct option: (2) 1716

• 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.