Final answer:
Due to the lack of specific data such as the initial length and temperature of the poker, along with the coefficient of linear expansion for iron, there is insufficient information to calculate the exact temperature of the fire based on the poker lengthening 0.30 cm.
Step-by-step explanation:
The question posed about the iron poker lengthening in a fireplace due to heat is related to thermal expansion and physical properties of materials. However, the amount of lengthening by 0.30 cm does not provide sufficient information to determine the fire's temperature without additional data such as the poker's original length, the coefficient of linear expansion, and the initial temperature.
From a physics perspective, and based on the other provided questions, which relate to the transfer of heat and temperature changes, we can link the phenomena by stating that as the temperature of the poker increases due to heat transfer from the fire, the atoms within the poker vibrate more vigorously and the metal expands. Yet, without knowing the precise coefficients and the starting conditions, we cannot use this information to calculate the exact temperature of the fire.