A car moving at a speed of 90 km / h consumes 5 liters of gasoline per hour.

| February 17, 2021 | education

A car moving at a speed of 90 km / h consumes 5 liters of gasoline per hour. Determine how much power is developed by the car engine, if its efficiency = 36%.

v = 90 km / h = 25 m / s.

t = 1 hour = 3600 s.

V = 5 l = 0.005 m3.

q = 4.6 * 107 J / kg.

ρ = 710 kg / m3.

Efficiency = 36%.

N -?

Efficiency = 36% means that 36% of the energy Qs, which is released during the combustion of gasoline, goes to the development of the traction force of the car, that is, to the useful energy Qp of the car.

Efficiency = Qp * 100% / Qz.

Qz = q * m.

m = V * ρ.

Qп = N * t.

Efficiency = N * t * 100% / q * V * ρ.

N = efficiency * q * V * ρ / t * 100%.

N = 36% * 4.6 * 107 J / kg * 0.005 m3 * 710 kg / m3 / 3600 s * 100% = 16630 W.

Answer: the car engine develops a power of N = 16630 W.



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