1
JEE Advanced 2020 Paper 2 Offline
Numerical
+3
-1
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A train with cross-sectional area St is moving with speed vt inside a long tunnel of cross-sectional area S0 (S0 = 4St). Assume that almost all the air (density $$\rho $$) in front of the train flows back between its sides and the walls of the tunnel. Also, the air flow with respect to the train is steady and laminar. Take the ambient pressure and that inside the train to be p0. If the pressure in the region between the sides of the train and the tunnel walls is p, then
p0 - p = $${7 \over {2N}}\rho v_t^2$$. The value of ЁЭСБ is ________.
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2
JEE Advanced 2020 Paper 2 Offline
Numerical
+3
-1
Change Language
Two large circular discs separated by a distance of 0.01 m are connected to a battery via a switch as shown in the figure. Charged oil drops of density 900 kg mтИТ3 are released through a tiny hole at the center of the top disc. Once some oil drops achieve terminal velocity, the switch is closed to apply a voltage of 200 V across the discs. As a result, an oil drop of radius 8 $$ \times $$ 10тИТ7 m stops moving vertically and floats between the discs. The number of electrons present in this oil drop is ________.
(neglect the buoyancy force, take acceleration due to gravity = 10 msтИТ2 and charge on an electron (e) = 1.6 $$ \times $$ 10тАУ19 C) JEE Advanced 2020 Paper 2 Offline Physics - Electrostatics Question 30 English
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3
JEE Advanced 2020 Paper 2 Offline
Numerical
+3
-1
Change Language
A point charge q of mass m is suspended vertically by a string of length l. A point dipole of dipole moment $$\overrightarrow p $$ is now brought towards q from infinity so that the charge moves away. The final equilibrium position of the system including the direction of the dipole, the angles and distances is shown in the figure below. If the work done in bringing the dipole to this position is N $$ \times $$ (mgh), where g is the acceleration due to gravity, then the value of N is _________ .
(Note that for three coplanar forces keeping a point mass in equilibrium, $${F \over {\sin \theta }}$$ is the same for all forces, where F is any one of the forces and $$\theta $$ is the angle between the other two forces) JEE Advanced 2020 Paper 2 Offline Physics - Electrostatics Question 29 English
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4
JEE Advanced 2020 Paper 2 Offline
Numerical
+3
-1
Change Language
A hot air balloon is carrying some passengers, and a few sandbags of mass 1 kg each so that its total mass is 480 kg. Its effective volume giving the balloon its buoyancy is V. The balloon is floating at an equilibrium height of 100 m. When N number of sandbags are thrown out, the balloon rises to a new equilibrium height close to 150 m with its volume V remaining unchanged. If the variation of the density of air with height h from the ground is
$$\rho \left( h \right) = {\rho _0}{e^{ - {h \over {{h_0}}}}}$$, where $$\rho $$0 = 1.25 kg mтИТ3 and h0 = 6000 m, the value of N is _________.
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