A cup of coffee cools from 90°C to 80°C in t minutes, when the room temperature is 20°C.
The time taken by a similar cup of coffee to cool from 80°C to 60°C at a room temperature same at 20°C is:
A cup of coffee cools from 90°C to 80°C in t minutes, when the room temperature is 20°C.
The time taken by a similar cup of coffee to cool from 80°C to 60°C at a room temperature same at 20°C is:
According to Newton's law of cooling
(T? -T? )/t = K [ (T? +T? )/2 - T? ]
For 1? cup of coffee,
(90-80)/t = K [ (90+80)/2 - 20]
For 2? cup of coffee,
(80-60)/t' = K [ (80+60)/2 - 20]
Divide (1) by (2)
t'/t = 65/50 ⇒ t' = (13/5)t
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