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 'T0'. It takes time 't1' to cool from 'T' to 'T2', time t2 to cool from 'T2' to 'T3' and time 't3' to cool from 'T3' to 'T4'. If (T - T2) = (T2 - T3) = (T3 - T4), then
- (A) t1 > t2 > t3
- (B) t1 = t2 = t3
- (C) t3> t2 > t1
- (D) t1 > t2 = t3
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 'α' respectively. When the rod is heated, the work performed is
- (A) 1/2 YALα²t²
- (B) 1/2 YAL²Î±²t²
- (C) 1/2 YALαt
- (D) YALαt
5. A metal rod of Young's modulus 'Y' and coefficient of linear expansion 'α' has its temeperature raised by '△θ'. The linear stress to prevent the expansion of rod is (L and l is original length of rod and expansion respectively)
- (A) Y ∝ △θ
- (B) Y(l/L)²
- (C) YL/l
- (D) Y∝/△θ
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 = 1011 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, α = coefficient of linear expansion of the rod.)
- (A) YAαT(1 - αT)
- (B) YAαT/(1 + αT)
- (C) YAα/T(1 + αT)
- (D) YAα/(1 - αT)
