1
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
2
JEE Main 2019 (Online) 12th January Evening Slot
+4
-1
A vertical closed cylinder is separated into two parts by a frictionless piston of mass m and of negligible thickness. The piston is free to move along the length of the cylinder. The length of the cylinder above the piston is $$\ell$$1, and that below the piston is $$\ell$$2, such that $$\ell$$1 > $$\ell$$2. Each part of the cylinder contains n moles of an ideal gas at equal temperature T. If the piston is stationary, its mass, m, will be given by :
(R is universal gas constant and g is the acceleration due to gravity)
A
$${{nRT} \over g}\left[ {{{{\ell _1} - {\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$$
B
$${{RT} \over g}\left[ {{{2{\ell _1} + {\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$$
C
$${{nRT} \over g}\left[ {{1 \over {{\ell _2}}} + {1 \over {{\ell _1}}}} \right]$$
D
$${{RT} \over {ng}}\left[ {{{{\ell _1} - 3{\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$$
3
JEE Main 2019 (Online) 12th January Morning Slot
+4
-1
An ideal gas occupies a volume of 2m3 at a pressure of 3 $$\times$$ 106 Pa. The energy of the gas is :
A
6 $$\times$$ 104 J
B
9$$\times$$ 106 J
C
3 $$\times$$ 102 J
D
108 J
4
JEE Main 2019 (Online) 12th January Morning Slot
+4
-1
A cylinder of radius R is surrounded by a cylindrical shell of inner radius R and outer radius 2R. The thermal conductivity of the material of the inner cylinder is K1 and the of the outer cylinder is K2. Assuming no loss of heat, the effective thermal conductivity of the system for heat flowing along the length of the cylinder is :
A
K1 + K2
B
$${{{K_1} + 3{K_2}} \over 4}$$
C
$${{{K_1} + {K_2}} \over 2}$$
D
$${{2{K_1} + 3{K_2}} \over 5}$$
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