A) 40 minute
B) 9 minute
C) 30 minute
D) 20 minute
Correct Answer: B
Solution :
According to Newtons law of cooling |
in first case,\[\frac{80-50}{5}=K\left[ \frac{80+50}{2}-20 \right]\] ..(i) |
in second case,\[\frac{60-30}{t}=k\left[ \frac{60+30}{2}-20 \right]\] (ii) |
Dividing equation (i) by (ii) we get, \[\frac{t}{2}=\frac{45}{25}\]\[\Rightarrow \]\[t=9\]min. |
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