Question

Temperature of the hotter sample is 96°c; temperature of the mixture is 36°, then change in temperature is_________​

Answer 1

Explanation:

Correct option is

B

2.8 minutes

Using Newton's law of cooling with approximation, dtdT=ms−k(Tavg−Ts)

Case 1 :  dt=2 minutes; Ts=20       

Tavg=294+86=90 and dT=94−86=8

∴   ms−k=dtdT.Tavg−Ts1=2×708=0.05714            

  

Tavg=274+66=70 and dT=74−66=8

∴ Time in which it cools down  dt8=0.05714×(70−20)

⟹ dt=

Answer 2

Answer:

60°

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