Horsepower is a unit commonly used to express which property of an engine?

• A. Weight
• B. Speed
• C. Torque
• D. Power

Answer: (D)

Power is the rate at which work is done, and horsepower is the unit used to express that property for engines. It tells you how quickly an engine can transfer energy to do work over time. Because power depends on both the turning force (torque) and how fast the engine rotates (RPM), horsepower captures the overall ability of an engine to perform work quickly. In practical terms, a higher horsepower means more work can be done per second, which is why engines are rated this way. The other concepts describe different things—weight is how heavy something is, speed is how fast it moves, and torque is the turning force alone—so they don’t convey the rate of doing work over time like horsepower does.