How much natural gas needs to be burned to perform useful work 110 kJ, if the engine efficiency

How much natural gas needs to be burned to perform useful work 110 kJ, if the engine efficiency is 25%, and the heat of combustion is 44 MJ per kg.

To calculate the mass of natural gas consumed, we apply the formula: η = Ap / Q = Ap / (qпг * m), whence m = Ap / (qпг * η).

Variables and constants: Ap – useful work performed (Ap = 110 kJ = 110 * 10 ^ 3 J); η (efficiency of the motor used) = 25% (0.25); qпг is the heat of combustion of natural gas (according to the condition qпг = 44 MJ / kg = 44 * 10 ^ 6 J / kg).

Let’s perform the calculation: m = Ap / (qпг * η) = 110 * 10 ^ 3 / (44 * 10 ^ 6 * 0.25) = 110 * 10 ^ 3 / (11 * 10 ^ 6) = 0.01 kg or 10 g

Answer: The mass of gas is 10 g.