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NEET-XI-Physics

exam-2 year:2016

with Solutions - page 3
Qstn# 128 Prvs-QstnNext-Qstn
  • #128
    A body cools from a temperature 3T to 2T in
    10 minutes. The room temperature is T. Assume
    that Newton's law of cooling is applicable. The
    temperature of the body at the end of next
    10 minutes will be :-
    (1)``\frac43`` T
    (2) T
    (3)``\frac74`` T
    (4)``\frac32`` T
    digAnsr:   4
    Ans : (4)
    Sol. Newton's laws of cooling
    1 2 1 2T T T Tk T
    t 2
     + 
    =  
     
    3T 2T 5T 2T
    k
    10 2
      
    =  
     
    &implies;
    T 3T
    k
    10 2
     
    =  
     
    ...(i)
    2T T ' 2T T '
    k T
    10 2
     + 
    =  
     
    &implies;
    2T T ' T '
    k
    10 2
      
    =  
     
    ...(ii)
    By solving (i) and (ii)
    3
    T ' T
    2
    =