Power equals resistive force times velocity at constant speed

Steps:

• At constant speed, net force is zero, so driving force equals total resistive force F.
• Output power P = F × v, where v is speed.
• Convert P to watts: 300 kW = 300,000 W; v = 80 m/s.
• Solve for F = P / v = 300,000 / 80 = 3,750 N = 3.75 kN.

Why A is correct:

• The formula P = F v yields 3.75 kN, which is closest to option A among the choices.

Why the others are wrong:

• B. 10 kN implies P = 10,000 × 80 = 800 kW, exceeding given power.
• C. 50 kN implies P = 50,000 × 80 = 4,000 kW, far too large.
• D. 100 kN implies P = 100,000 × 80 = 8,000 kW, unrealistic for the car.

Final answer: A