# How much dry wood must be burned to obtain an amount of heat equal to the heat released during

How much dry wood must be burned to obtain an amount of heat equal to the heat released during the combustion of 20 liters of gasoline?

Vben = 20 l = 0.02 m ^ 3.
ρben = 710 kg / m ^ 3.
λdr = 1 * 10 ^ 7 J / kg.
λben = 4.6 * 10 ^ 7 J / kg.
mdr -?
Let us write down the amount of heat that is released during the combustion of gasoline and firewood: Qben = λben * mben, Qdr = λdr * mdr, where mben, mdr are the masses of burned gasoline and firewood, λben, λdr is the specific heat of combustion of gasoline and firewood.
mben = Vben * ρben.
λben * Vben * ρben = λdr * mdr.
mdr = λben * Vben * ρben / λdr.
mdr = 4.6 * 10 ^ 7 J / kg * 0.02 m ^ 3 * 710 kg / m ^ 3/1 * 10 ^ 7 J / kg = 65.3 kg.
Answer: you need to burn mdr = 65.3 kg of firewood.

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