1
JEE Main 2020 (Online) 5th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A spaceship in space sweeps stationary interplanetary dust. As a result, its mass
increases at a rate $${{dM\left( t \right)} \over {dt}}$$ = bv2(t), where v(t) is its instantaneous velocity. The instantaneous acceleration of the satellite is :
A
-bv3(t)
B
$$ - {{2b{v^3}} \over {M\left( t \right)}}$$
C
$$ - {{b{v^3}} \over {M\left( t \right)}}$$
D
$$ - {{b{v^3}} \over {2M\left( t \right)}}$$
2
JEE Main 2020 (Online) 5th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The quantities x = $${1 \over {\sqrt {{\mu _0}{\varepsilon _0}} }}$$, y = $${E \over B}$$ and z = $${l \over {CR}}$$ are
defined where C-capacitance, R-Resistance, l-length, E-Electric field, B-magnetic field and $${{\varepsilon _0}}$$, $${{\mu _0}}$$, - free space permittivity and permeability respectively. Then :
A
Only y and z have the same dimension
B
x, y and z have the same dimension
C
Only x and y have the same dimension
D
Only x and z have the same dimension
3
JEE Main 2020 (Online) 5th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Ten charges are placed on the circumference of a circle of radius R with constant angular separation between successive charges. Alternate charges 1, 3, 5, 7, 9 have charge (+q) each, while 2, 4, 6, 8, 10 have charge (–q) each. The potential V and the electric field E at the centre of the circle are respectively.
(Take V = 0 at infinity)
A
V = 0; E = 0
B
$$V = {{10q} \over {4\pi {\varepsilon _0}R}}$$; $$E = {{10q} \over {4\pi {\varepsilon _0}{R^2}}}$$
C
$$V = {{10q} \over {4\pi {\varepsilon _0}R}}$$; E = 0
D
V = 0; $$E = {{10q} \over {4\pi {\varepsilon _0}{R^2}}}$$
4
JEE Main 2020 (Online) 5th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The correct match between the entries in column I and column II are :

I II
Radiation Wavelength
(a) Microwave (i) 100 m
(b) Gamma rays (ii) 10–15 m
(c) A.M. radio waves (iii) 10–10 m
(d) X-rays (iv) 10–3 m
A
(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
B
(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
C
(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
D
(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
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