TG EAMCET 2 May 2025 Shift 2 Paper

According to Newton's law of cooling.
‌

T1−T2

t

=K(‌

T1+T2

2

−T0)
For the first case
‌‌

60−50

10

=K(‌

60+50

2

−T0)
‌1=K(55−T0)
For the second case
‌‌

50−40

15

=K(‌

50+40

2

−T0)
⇒‌

10

15

=K(45−T0)
‌‌

2

3

=K(45−T0)
Dividing Eqs. (i) by Eq. (ii), we get
‌

1

2∕3

‌=‌

55−T0

45−T0

‌

3

2

‌=‌

55−T0

45−T0

⇒‌‌T0‌=25∘C
∴ From Eq. (i), 1=K(55−25),
⇒K=‌

1

30

If t be the time taken to cool from 40∘C to 30∘C, then
‌‌‌‌

40−30

t

=K(‌

40+30

2

−T0)
‌‌‌‌

10

t

=(‌

1

30

)(35−25)
‌⇒t=30‌ minutes ‌