Determine the efficiency of the motorcycle engine if it consumes 8 liters of gasoline for 1 hour of operation.

Determine the efficiency of the motorcycle engine if it consumes 8 liters of gasoline for 1 hour of operation. Engine power 70 kW.

Given: SI:

t = 1 h = 3600 s.

λ = 4.6 * 10 ^ 7 J / kg.

V = 8 l = 8 * 10 ^ -3 m ^ 3.

ρ = 700 kg / m ^ 3.

N = 70 kW = 70 * 10 ^ 3 J.

Efficiency -?

Solution:

Let us write down the definitions for the efficiency of a motorcycle: efficiency = Ep * 100% / Ez, where Ep is the useful energy, Ez is the consumed energy, the energy that is released during the combustion of gasoline.

Ez = λ * m, where λ is the specific heat of combustion of gasoline, m is the mass of gasoline that burns in the engine.

m = ρ * V.

Ez = λ * ρ * V.

Useful energy Еп is expressed by the formula: Еп = N * t.

The formula for determining the efficiency will take the form: efficiency = N * t * 100% / λ * ρ * V.

Efficiency = 70 * 10 ^ 3 J * 3600 s * 100% / 4.6 * 10 ^ 7 J / kg * 700 kg / m ^ 3 * 8 * 10 ^ -3 m ^ 3 = 97.8%.

Answer: The motorcycle has an efficiency of 97.8%.