Question 759: Thermodynamics & KTG

Question

A metal rod cools at the rate of $4{ }^{\circ} \mathrm{C} / \mathrm{min}$ whon its temperature is $90^{\circ} \mathrm{C}$ and the rate of $1{ }^{\circ} \mathrm{C} / \mathrm{m}{	ext {in }}$ when its temperature is $30^{\circ} \mathrm{C}$. The temperature of the surrounding is

Accepted Answer

According to Newton's law of cooling,
$\begin{aligned}
& \frac{\mathrm{R}_1}{\mathrm{R}_2}=\frac{	heta_1-	heta_0}{	heta_2-	heta_0} \
	herefore \quad & \frac{4}{1}=\frac{90-	heta_0}{30-	heta_0} \
	herefore \quad & 120-90=4 	heta_0-	heta_0 \
	herefore \quad & 3 	heta_0=30
\end{aligned}$
$	herefore \quad$ Temperature of the surroundings is,
$	heta_0=10^{\circ} \mathrm{C}$

Answer

$20^{\circ} \mathrm{C}$

Answer

$15{ }^{\circ} \mathrm{C}$

Answer

$10^{\circ} \mathrm{C}$

Answer

$5^{\circ} \mathrm{C}$

Thermodynamics & KTG

A metal rod cools at the rate of 4{ }^{\circ} \mathrm{C} / \mathrm{min} whon its temperature is 90^{\circ} \mathrm{C} and the rate of 1{ }^{\circ} \mathrm{C} / \mathrm{m}{\text{in }} when its temperature is 30^{\circ} \mathrm{C}. The temperature of the surrounding is

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