1
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+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 Evening Slot
MCQ (Single Correct Answer)
+4
-1
Assuming the nitrogen molecule is moving with r.m.s. velocity at 400 K, the de-Broglie wavelength of nitrogen molecule is close to :
(Given : nitrogen molecule weight : 4.64 $$ \times $$ 10–26 kg,
Boltzman constant: 1.38 $$ \times $$ 10–23 J/K,
Planck constant : 6.63 $$ \times $$ 10–34 J.s)
A
0.44 $$\mathop A\limits^o $$
B
0.34 $$\mathop A\limits^o $$
C
0.20 $$\mathop A\limits^o $$
D
0.24 $$\mathop A\limits^o $$
3
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
The linear mass density of a thin rod AB of length L varies from A to B as
$$\lambda \left( x \right) = {\lambda _0}\left( {1 + {x \over L}} \right)$$, where x is the distance from A. If M is the mass of the rod then its moment of inertia about an axis passing through A and perpendicular to the rod is :
A
$${2 \over 5}M{L^2}$$
B
$${5 \over {12}}M{L^2}$$
C
$${7 \over {18}}M{L^2}$$
D
$${3 \over 7}M{L^2}$$
4
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity K1 , K2 and K3 , respecrtively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at 100oC and the other at 0oC (see figure). If the joints of the rod are at 70oC and 20oC in steady state and there is no loss of energy from the surface of the rod, the correct relationship between K1 , K2 and K3 is : JEE Main 2020 (Online) 6th September Evening Slot Physics - Heat and Thermodynamics Question 207 English
A
K1 : K3 = 2 : 3,
K2 : K3 = 2 : 5
B
K1 < K2 < K3
C
K1 : K2 = 5 : 2,
K1 : K3 = 3 : 5
D
K1 > K2 > K3
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