What is the formula for calculating Output RPM?

• A. Input RPM/Output RPM = Output Diameter/Input Diameter
• B. Output RPM = Input RPM × (Output Diameter/Input Diameter)
• C. Output RPM = Input RPM + (Output Diameter/Input Diameter)
• D. Output RPM = Input RPM - (Output Diameter/Input Diameter)

Answer: (B)

The formula for calculating Output RPM correctly relates the input speed of a system to the diameters of the input and output components. In this case, the correct choice states that Output RPM is calculated by multiplying the Input RPM by the ratio of the Output Diameter to the Input Diameter.

This formula comes from the principle of conservation of power in a mechanical system, where the speed (RPM) and diameters are inversely proportional. When the output diameter increases relative to the input diameter, the output speed decreases, and vice versa. By using the correct proportion, multiplying the Input RPM by the ratio ensures that you adjust for the change in diameters appropriately and yields the correct Output RPM. Thus, the formula accurately represents the relationship between the rotational speeds and diameters in systems like gears or pulleys, where the diameter directly influences the RPM.