1
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
A massless spring (k = 800 N/m), attached with a mass (500 g) is completely immersed in 1 kg of water. The spring is stretched by 2 cm and released so that it starts vibrating. What would be the order of magnitude of the change in the temperature of water when the vibrations stop completely ? (Assume that the water container and spring receive negligible heat and specific heat of mass = 400 J/kg K, specific heat of water = 4184 J/kg K)
A
10–3 K
B
10–1 K
C
10–5K
D
10–4 K
2
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
The specific heats, CP and CV of a gas of diatomic molecules, A, are given (in units of J mol–1 K–1) by 29 and 22, respectively. Another gas of diatomic molecules, B, has the corresponding values 30 and 21. If they are treated as ideal gases, then :-
A
A is rigid but B has a vibrational mode
B
A has a vibrational mode but B has none
C
A has one vibrational mode and B has two
D
Both A and B have a vibrational mode each
3
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Two materials having coefficients of thermal conductivity '3K' and 'K' and thickness 'd' and '3d', respectively, are joined to form a slab as shown in the figure. The temperatures of the outer surfaces are '$$\theta $$2' and '$$\theta $$1' respectively, ($$\theta $$2 > $$\theta $$1). The temperature at the interface is :-

JEE Main 2019 (Online) 9th April Evening Slot Physics - Heat and Thermodynamics Question 261 English
A
$${{{\theta _1}} \over {10}} + {{9{\theta _2}} \over {10}}$$
B
$${{{\theta _2} + {\theta _1}} \over 2}$$
C
$${{{\theta _1}} \over {6}} + {{5{\theta _2}} \over {6}}$$
D
$${{{\theta _1}} \over {3}} + {{2{\theta _2}} \over {3}}$$
4
JEE Main 2019 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
An HCl molecule has rotational, translational and vibrational motions. If the rms velocity of HCl molecules in its gaseous phase is $$\overline v $$ , m is its mass and kB is Boltzmann constant, then its temperature will be :
A
$${{m{{\overline v }^2}} \over {5{k_B}}}$$
B
$${{m{{\overline v }^2}} \over {6{k_B}}}$$
C
$${{m{{\overline v }^2}} \over {7{k_B}}}$$
D
$${{m{{\overline v }^2}} \over {3{k_B}}}$$
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