**MHT-CET 2005**

*1*. A body cools from 100°C to 70°C in 8 s. If the room temperature is 15°C and assuming Newton's law of cooling holds good, then time required for the body to cool from 70°C to 40°C is

**(A) 14 s**- (B) 8 s
- (C) 10 s
- (D) 5 s

**MHT-CET 2006**

*2*. Newton's law of cooling holds good only. if the temperature difference between the body and the surroundings is

**(A) less than 10°C**- (B) more than 10°C
- (C) less than 100°C
- (D) more than 100'C

**MHT-CET 2019**

*3*. A hot body at a temperature 'T' is kept in a surrounding of temperature 'T_{0}'. It takes time 't_{1}' to cool from 'T' to 'T_{2}', time t_{2} to cool from 'T_{2}' to 'T_{3}' and time 't_{3}' to cool from 'T_{3}' to 'T_{4}'. If (T - T_{2}) = (T_{2} - T_{3}) = (T_{3} - T_{4}), then

- (A) t
_{1}> t_{2}> t_{3} - (B) t
_{1}= t_{2}= t_{3} **(C) t**_{3}> t_{2}> t_{1}- (D) t
_{1}> t_{2}= t_{3}

**MHT-CET 2020**

*4*. A metal rod is heated to t°C. A metal rod has length. area of cross-section. Young's modulus and coefficient of linear expansion as 'L', 'A', 'Y' and **'**Î±' respectively. When the rod is heated, the work performed is

**(A) 1/2 YALÎ±²t²**- (B) 1/2 YAL²Î±²t²
- (C) 1/2 YALÎ±t
- (D) YALÎ±t

*5*. A metal rod of Young's modulus 'Y' and coefficient of linear expansion 'Î±' has its temeperature raised by '**△**Î¸'. The linear stress to prevent the expansion of rod is (L and l is original length of rod and expansion respectively)

**(A) Y ∝ △Î¸**- (B) Y(l/L)²
- (C) YL/l
- (D) Y∝/
**△**Î¸

*6*. A metal rod of cross-sectional area 3 x 10^{-6} m² is suspended vertically from one end has a length 0.4 m at 100°C. Now the rod is cooled upto 0°C, but prevented from contracting by attaching a mass 'm' at the lower end. The value of 'm' is (Y = 10^{11} N/m²), coefficient of linear expansion = 10^{-5}/K, g = 10 m/s²)

**(A) 30 kg**- (B) 40 kg
- (C) 20 kg
- (D) 10 kg

*7*. A metal rod of length L and cross-sectional area A is heated through T °C. What is the force required to prevent the expansion of the rod lengthwise? (Y = Young's modulus of material of the rod, Î± = coefficient of linear expansion of the rod.)

- (A) YAÎ±T(1 - Î±T)
**(B) YAÎ±T/(1 + Î±T)**- (C) YAÎ±/T(1 + Î±T)
- (D) YAÎ±/(1 - Î±T)