___________ occurs when two gears of equal size turn without changing torque or speed.

This phenomenon is referred to as "gear meshing" or "gear engagement." When two gears of equal size, also known as spur gears, are engaged, they will turn in opposite directions. Since the gears are of equal size, they will maintain the same rotational speed and torque throughout the engagement.

This principle is crucial in mechanical engineering and machinery design, as it allows for the smooth transfer of motion and power from one gear to another. The setup helps ensure that the mechanical advantage is maintained without any loss in speed or force, which is essential for efficient operation in various applications, such as clocks, vehicles, and industrial machinery.

In summary, when two gears of equal size turn within a gear system, it promotes effective energy transfer while maintaining torque and speed, which is vital for optimal performance in mechanical systems.