Mechanical–electrical equivalence: Evaluate the statement “One horsepower equals 746 watts.” Choose the most accurate assessment for engineering calculations.

Introduction / Context:
Power conversions between imperial and SI units are common in motors, generators, and mechanical drives. Horsepower (hp) is frequently converted to watts (W) to compare specifications or compute energy consumption.

Given Data / Assumptions:

• Using mechanical (imperial) horsepower.
• Steady power; no efficiency correction included.
• Standard engineering approximation is acceptable.

Concept / Approach:
By definition, 1 mechanical horsepower ≈ 550 ft·lbf/s. Converting to SI: 1 ft = 0.3048 m and 1 lbf = 4.4482216 N, so 1 hp ≈ 550 * 4.4482216 * 0.3048 W ≈ 745.7 W. In practice, engineers round to 746 W for quick calculations. Electrical horsepower used by some utilities is also set to 746 W for convenience.

Step-by-Step Solution:

Verification / Alternative check:
Check motor nameplates: power is often given in hp and kW, with 1 hp listed near 0.746 kW. This cross-verifies the standard equivalence.

Why Other Options Are Wrong:

• Exactly 1000 W (option b) confuses horsepower with kilowatt.
• ≈ 550 W (option c) confuses force–distance units with power directly.
• “Unit of energy” (option d) is incorrect; horsepower is a rate (power), analogous to watts.

Common Pitfalls:
Mixing metric horsepower (PS ≈ 735.5 W) with mechanical horsepower; both are close but not identical. Always check which definition applies.

Final Answer:
Correct — 1 hp ≈ 746 W.