Solved Problem on Heat
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FR
PT-BR
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A body has a mass of 500 grams and a specific heat of 0.4 cal/g°C. Determine:
a) The quantity of heat that the body should receive to ensure that its temperature varies from 5 °C to 35 °C;
b) The quantity of heat that the body must give so its temperature decreases from 15 °C.
Problem data:
- Mass of body: m = 500 g;
- Specific heat: c = 0.4 cal/g°C.
a) The initial temperature ti = 5 °C and the final temperature tf = 35 °C, the quantity of heat that the body should receive to occur heating will be given by the equation heat
\[
\begin{gather}
\bbox[#99CCFF,10px]
{Q=mc\Delta t} \tag{I}
\end{gather}
\]
\[
\begin{gather}
Q=mc(t_f-t_i) \\[5pt]
Q=(500\;\mathrm{\cancel g})\left(0.4\;\mathrm{\small{\frac{cal}{\cancel g\cancel{°C}}}}\right)(35-5)\;\mathrm{\cancel{°C}} \\[5pt]
\end{gather}
\]
\[
\begin{gather}
\bbox[#FFCCCC,10px]
{Q=6000\;\mathrm{cal}}
\end{gather}
\]
b) If the heat is lost Δt<0, therefore the variation should be Δt = −15 °C, and the lost heat will be given using the equation (I)
\[
\begin{gather}
Q=mc\Delta t \\[5pt]
Q=(500\;\mathrm{\cancel g})\left(0.4\;\mathrm{\small{\frac{cal}{\cancel g\cancel{°C}}}}\right)(-15)\;\mathrm{\cancel{°C}} \\[5pt]
\end{gather}
\]
\[
\begin{gather}
\bbox[#FFCCCC,10px]
{Q=-3000\;\mathrm{cal}}
\end{gather}
\]
Note: in item (a), the temperature varies from an initial value ti
to a final value tf, we know the initial and final values of the temperature.
In item (b), the temperature varies from a certain value, we know the variation Δt
without knowing the values initial and final of the temperature.
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Fisicaexe - Physics Solved Problems by Elcio Brandani Mondadori is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License .