Question 284: Properties of Matter

Question

In an experiment to verify Newton's law of cooling, a graph is plotted between the temperature difference ($$\Delta$$T) of the water and surroundings and time as shown in figure. The initial temperature of water is taken as 80$$^\circ$$C. The value of t2 as mentioned in the graph will be __________.

Accepted Answer

Temperature of surrounding = 20$$^\circ$$C
For 0 $$	o$$ 6 minutes, average temp. = 70$$^\circ$$C
$$	o$$ Rate of cooling $$\propto$$ 70$$^\circ$$C $$-$$ 20$$^\circ$$C = 50$$^\circ$$C
For 6 $$	o$$ t
2
minutes, average temp. = 50$$^\circ$$C
$$	o$$ Rate of cooling $$\propto$$ 30$$^\circ$$C
$$ \Rightarrow {t_2} - 6 = {5 \over 3}$$ (6 minutes)
$$\Rightarrow$$ t
2
= 16 minutes

Properties of Matter

In an experiment to verify Newton's law of cooling, a graph is plotted between the temperature difference ($\DeltaT) of the water and surroundings and time as shown in figure. The initial temperature of water is taken as 80^\circ$C. The value of t2 as mentioned in the graph will be __________.

Choose the correct answer: