1
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
If the constant term in the binomial expansion of
$${\left( {\sqrt x - {k \over {{x^2}}}} \right)^{10}}$$ is 405, then |k| equals :
A
3
B
9
C
1
D
2
2
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Let $$\theta = {\pi \over 5}$$ and $$A = \left[ {\matrix{ {\cos \theta } & {\sin \theta } \cr { - \sin \theta } & {\cos \theta } \cr } } \right]$$.

If B = A + A4 , then det (B) :
A
lies in (1, 2)
B
lies in (2, 3).
C
is zero.
D
is one.
3
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
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 $$\mathop A\limits^o $$
4
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
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
$${3 \over 7}M{L^2}$$
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