A common method of converting rotary motion to linear motion is using ____________.

• A. Rack and Pinion
• B. Bevel Gear
• C. Planetary Gear
• D. Helical

Answer: (A)

Directly turning rotation into straight-line motion is best accomplished with a rack-and-pinion. The pinion—a small gear—meshes with a linear rack, a bar with matching teeth. As the pinion rotates, its teeth push against the rack, converting circular motion into linear displacement of the rack. The amount the rack moves per revolution depends on the gear’s pitch and teeth count, giving a predictable, almost 1:1 relationship in many designs. This simple, robust arrangement is why rack-and-pinion is so common in steering systems, CNC tables, and other linear actuation tasks. Bevel gears redirect motion between shafts, planetary gear trains change torque/speed while keeping rotation, and helical gears transmit rotary motion smoothly but don’t inherently produce linear motion unless paired with another mechanism.