To maintain a speed of 80 km h - 1 by a bus of mass 500 kg on a plane rough road for 4 km distance, the work done by the engine of the bus will be _____ kJ . [The coefficient of friction between tyre of bus and road is 0 . 04 ]

Step-by-step solution

It is given, v = 80   km   h - 1 m = 500   kg S = 4   km μ = 0 . 04 The power due to friction is P f = F v where F = μ m g = 0 . 04 500 × 9 . 8 × 80 × 5 18   W Hence, the work done by the engine in overcoming the friction is W = P f t = P f d v ⇒ W = 20 × 9 . 8 × 80 × 5 18 × 4 × 10 3 80 × 5 18 = 784   kJ