Define gear ratio.

The correct definition of gear ratio is the ratio of the number of teeth on the input gear to the output gear. This value determines how the rotational speeds and torque are modified between the input and output gears in a mechanical system.

When you consider a gear system, the gear ratio influences how much the input gear's rotation translates into output gear movement. If the input gear has more teeth compared to the output gear, the output will rotate faster, while if it has fewer teeth, the output will turn slower but with greater torque. This relationship is crucial for designing mechanical systems where specific speed and torque requirements must be met, illustrating how power is transmitted through different gear configurations.

Understanding gear ratios is essential in many applications, from automotive transmissions to industrial machinery, as they fundamentally affect performance and efficiency.