A) 4 min
B) 2 min
C) 6 min
D) 8 min
Correct Answer: C
Solution :
According to Newton's cooling law, \[\frac{{{\theta }_{1}}-{{\theta }_{2}}}{t}=K\left( \frac{{{\theta }_{1}}+{{\theta }_{2}}}{2}-\theta \right)\] \[\therefore \] \[\frac{61-59}{4}=K\left( \frac{61+59}{2}-30 \right)\] \[\Rightarrow \] \[K=\frac{1}{60}\] \[\frac{51-49}{t}=\frac{1}{60}\left( \frac{51+49}{2}-30 \right)\] \[t=6\text{ }min.\]You need to login to perform this action.
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