In the formula power = (torque x speed) / constant, the constant is used to convert units when speed is measured in RPM.

• A. To convert RPM to radians per second and apply unit conversions
• B. To adjust for efficiency
• C. To convert torque into horsepower
• D. To convert RPM to horsepower

Answer: (A)

Power is torque times angular speed, so to use RPM you must convert that speed into radians per second. Angular velocity in rad/s is RPM × (2π/60). Substituting into P = τ × ω gives P = τ × RPM × (2π/60) = (τ × RPM) ÷ (60/(2π)). The constant in the formula therefore represents the unit conversion that turns RPM into rad/s (and yields power in watts). That’s why this option is correct: it acknowledges both the angular velocity conversion and the resulting consistent power units. The other ideas don’t fit because they don’t address converting RPM to the proper angular-speed unit needed for the power calculation, or they misstate what is being converted.