1
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A solid sphere, of radius R acquires a terminal velocity v1 when falling (due to gravity) through a viscous fluid having a coefficient of viscosity . The sphere is broken into 27 identical solid spheres. If each of these spheres acquires a terminal velocity, v2, when falling through the same fluid, the ratio (v1/v2) equals :
A
$${1 \over 9}$$
B
$${1 \over {27}}$$
C
27
D
9
2
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
The number density of molecules of a gas depends on their distance r from the origin as, $$n\left( r \right) = {n_0}{e^{ - \alpha {r^4}}}$$. Then the total number of molecules is proportional to :
A
$${n_0}{\alpha ^{ - 3/4}}$$
B
$${n_0}{\alpha ^{ - 3}}$$
C
$${n_0}{\alpha ^{1/4}}$$
D
$$\sqrt {{n_0}} {\alpha ^{1/2}}$$
3
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A uniform cylindrical rod of length L and radius r, is made from a material whose Young’s modulus of Elasticity equals Y. When this rod is heated by temperature T and simultaneously subjected to a net longitudinal compressional force F, its length remains unchanged. The coefficient of volume expansion, of the material of the rod, is (nearly) equal to :
A
$${{3F} \over {\left( {\pi {r^2}YT} \right)}}$$
B
$${{6F} \over {\left( {\pi {r^2}YT} \right)}}$$
C
$${F \over {\left( {3\pi {r^2}YT} \right)}}$$
D
$${9F\left( {\pi {r^2}YT} \right)}$$
4
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
At 40o C, a brass wire of 1 mm radius is hung from the ceiling. A small mass, M is hung from the free end of the wire. When the wire is cooled down from 40oC to 20oC it regains its original length of 0.2 m. The value of M is close to : (Coefficient of linear expansion and Young’s modulus of brass are 10–5 /oC and 1011 N/m 2 , respectively; g= 10 ms–2 )
A
1.5 kg
B
0.5 kg
C
9 kg
D
0.9 kg
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Modern Physics
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