A tractor engine develops 45 kW of power at the drawbar. If it pulls a plough that requires a draft force of 9 kN, what is the operating speed of the tractor?

Power = Force × Velocity, so Velocity = Power ÷ Force = 45,000 W ÷ 9,000 N = 5 m/s. Converting to km/h: 5 m/s × 3.6 = 18 km/h. Wait — the answer should be 18 km/h. Rechecking: 45 kW = 45,000 W; 9 kN = 9,000 N; V = 45,000/9,000 = 5 m/s = 18 km/h. Answer is C.