Which of the following is a common type of gear?

• A. Spur
• B. Wheel
• C. Pulley
• D. Motor

Answer: (A)

Transmitting rotational motion between shafts with teeth is what defines a gear. A spur gear uses straight teeth that run parallel to the axis and meshes with another gear on a parallel shaft. This simple, straightforward geometry makes spur gears easy to manufacture, easy to align, and highly reliable for transferring torque with high efficiency across a wide range of speeds and loads. Because the teeth are straight and the gears lie on parallel axes, the design is compact, cost-effective, and well-suited for many standard gear trains found in robotics, clocks, and machinery.

Other options aren’t gears themselves: a wheel is a general rotating disk, not a gear with meshing teeth; a pulley uses belts to transmit motion rather than meshing teeth; a motor is a power source that drives gears rather than a type of gear. That’s why spur gears are the common gear type.