Question

A bus weighing 100 quintals moves on a rough road with a constant speed of 72km/h. The friction of the road is 9% of its weight and that of air is 1% of its weight. What is the power of the engine. Take g = 10m/s²

• A. 50 Kw
• B. 100 Kw
• C. 150 kW
• D. 200 Kw

Answer 1

Answer: (D)

200 Kw

Answer 2

Weight of a bus = mass × g

$= 100 \times 100kg \times 10m ⥂ / ⥂ s^{2} = 10^{5}N$

Total friction force = 10% of weight = 10⁴ N

∴ Power = Force × velocity

$= 10^{4}N \times 72km/h = 10^{4} \times 20watt = 2 \times 10^{5}watt = 200kW$.