How much dry wood needs to be burned to melt the stubborn tin soldier. The soldier weighs 5 kg, and his initial temperature is 12 degrees. Neglect the loss of energy.
λd = 1 * 10 ^ 7 J / kg.
mс = 5 kg.
Co = 230 J / kg * ° C.
kо = 59000 J / kg.
t1 = 12 ° C.
tm = 232 ° C.
When dry firewood is burned, the amount of heat Q is released, which is determined by the formula:
Q = λd * md, where λd is the specific heat of combustion of firewood, md is the mass of firewood.
Let us express the amount of heat Q required to heat the soldier to the melting point and melt it.
Q = Co * mc * (tm – t1) + ko * mc, where Co is the specific heat of tin, mc is the mass of the soldier, tm is the melting point of tin, t1 is the initial temperature of the soldier, ko is the specific heat of fusion of tin.
Let’s write down the heat balance equation: λd * md = Co * mc * (tpl – t1) + ko * mc.
md = (Co * mc * (tm – t1) + ko * mc) / λd.
md = (230 J / kg * ° C * 5 kg * (232 ° C – 12 ° C) + 59000 J / kg * 5 kg) / 1 * 10 ^ 7 J / kg = 0.0548 kg.
Answer: to melt a soldier, you need md = 0.0548 kg of dry firewood.
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