1
JEE Main 2019 (Online) 8th April Evening Slot
+4
-1
The temperature, at which the root mean square velocity of hydrogen molecules equals their escape velocity from the earth, is closest to :
[Boltzmann Constant kB = 1.38 × 10–23 J/K Avogadro Number NA = 6.02 × 1026 /kg Radius of Earth : 6.4 × 106 m Gravitational acceleration on Earth = 10ms–2]
A
3 × 105 K
B
104 K
C
650 K
D
800 K
2
JEE Main 2019 (Online) 8th April Morning Slot
+4
-1
Two identical beakers A and B contain equal volumes of two different liquids at 60°C each and left to cool down. Liquid in A has density of 8 × 102 kg/m3 and specific heat of 2000 J kg–1 K–1 while liquid in B has density of 103 kg m–3 and specific heat of 4000 J kg–1 K–1. Which of the following best describes their temperature versus time graph schematically? (assume the emissivity of both the beakers to be the same)
A
B
C
D
3
JEE Main 2019 (Online) 8th April Morning Slot
+4
-1
A thermally insulated vessel contains 150g of water at 0°C. Then the air from the vessel is pumped out adiabatically. A fraction of water turns into ice and the rest evaporates at 0°C itself. The mass of evaporated water will be closest to : (Latent heat of vaporization of water = 2.10 × 106 J kg–1 and Latent heat of Fusion of water = 3.36 × 105 J kg–1)
A
35 g
B
130 g
C
20 g
D
150 g
4
JEE Main 2019 (Online) 12th January Evening Slot
+4
-1
An ideal gas is enclosed in a cylinder at pressure of 2 atm and temperature 300 K. The mean time between two successive collisions is 6 $$\times$$ 10–8 s. If the pressure is doubled and temperature is increased to 500 K, the mean time between two successive collisions will be close to
A
0.5 $$\times$$ 10$$-$$8 s
B
4 $$\times$$ 10$$-$$8 s
C
3 $$\times$$ 10$$-$$6 s
D
2 $$\times$$ 10$$-$$7 s
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