1
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
A fluid is flowing through a horizontal pipe of varying cross-section, with
speed v ms–1 at a point where the pressure is P pascal. At another point where pressure is $${P \over 2}$$ Pascal its speed is V ms–1. If the density of the fluid is $$\rho$$ kg m–3 and the flow is streamline, then V is equal to :
A
$$\sqrt {{P \over {2\rho }} + {v^2}}$$
B
$$\sqrt {{P \over \rho } + {v^2}}$$
C
$$\sqrt {{{2P} \over \rho } + {v^2}}$$
D
$$\sqrt {{P \over \rho } + {v}}$$
2
JEE Main 2020 (Online) 6th September Morning Slot
+4
-1
An object of mass m is suspended at the end of a massless wire of length L and area of crosssection A. Young modulus of the material of the wire is Y. If the mass is pulled down slightly its frequency of oscillation along the vertical direction is :
A
$$f = {1 \over {2\pi }}\sqrt {{{YA} \over {mL}}}$$
B
$$f = {1 \over {2\pi }}\sqrt {{{mL} \over {YA}}}$$
C
$$f = {1 \over {2\pi }}\sqrt {{{YL} \over {mA}}}$$
D
$$f = {1 \over {2\pi }}\sqrt {{{mA} \over {YL}}}$$
3
JEE Main 2020 (Online) 5th September Evening Slot
+4
-1
In an experiment to verify Stokes law, a small spherical ball of radius r and density $$\rho$$ falls under gravity through a distance h in air before entering a tank of water. If the terminal velocity of the ball inside water is same as its velocity just before entering the water surface, then the value of h is proportional to :
(ignore viscosity of air)
A
r
B
r4
C
r3
D
r2
4
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
A hollow spherical shell at outer radius R floats just submerged under the water surface. The inner radius of the shell is r. If the specific gravity of the shell material is $${{27} \over 8}$$ w.r.t water, the value of r is :
A
$${{2} \over 3}$$R
B
$${{4} \over 9}$$R
C
$${{1} \over 3}$$R
D
$${{8} \over 9}$$R
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