15.
If the surrounding air is kept at 20°C and a body
cools from 80°C to 70°C in 5 minutes, the
temperature of the body after 15 minutes will be
(A) 51.7°C
(C) 52.7° C
(B) 54.7°C
(D) 50.7° C
Answers
Answered by
0
Step-by-step explanation:
Newton's cooling law
dt
dθ
=−k(θ−θ
0
)
putting the given values of the situation in the formula we get:-
5
(70−50)
=−k(70−20)
=>
5
20
=−k(50)
=>−k=
25
2
now, cooling body at 50
0
C for 10 min
let temperature after 10 min be T
10
(50−T)
=
25
2
(50−20)
10
(50−T)
=
5
12
50−T=24
T=50−24
T=26
0
C
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