The force required to tow a vehicle at constant velocity is directly proportional to the magnitude of velocity raised to the first power. It requires 1000 W to tow with a velocity of 10 m/s. How much power is required to tow at a velocity of 8 m/s?

(a) 320 W

(b) 640 W

(c) 160 W

(d) 80 W

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Correct option is (b) 640 W

To elaborate: Since force is directly proportional to velocity, the power required will be directly proportional to the square of the velocity.

Power = Force x Velocity

Hence, power is a multiple of 8^2 and an integer such that;

1000/10^2 = P/8^2

P = 640 W.