JEE Main · 2023 · 12 Apr 2023 · Shift 1 · Work, Power & Energy

To maintain a speed of

80 km / h

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].

Answer: 784

Solution

At constant speed the kinetic energy does not change, so by the work–energy theorem the engine's work just balances the work done against friction,

W = μ m g d

. With

μ = 0.04

m = 500 kg

g = 9.8 m s^{- 2}

and

d = 4 km = 4000 m

W = 0.04 \times 500 \times 9.8 \times 4000 = 7.84 \times 1 0^{5} J

. The work done by the engine is

784 kJ

JEE Main · 2023 · 12 Apr 2023 · Shift 1 · Integer answer

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