1
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
A large block of wood of mass M = 5.99 kg is hanging from two long massless cords. A bullet of mass m = 10 g is fired into the block and gets embedded in it. The (block + bullet) then swing upwards, their centre of mass rising a vertical distance h = 9.8 cm before the (block + bullet) pendulum comes momentarily to rest at the end of its arc. The speed of the bullet just before collision is :
(take g = 9.8 ms-2)

A
831.4 m/s
B
811.4 m/s
C
841.4 m/s
D
821.4 m/s
2
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
Four equal masses, m each are placed at the comers of a square of length (l) as shown in the figure. The moment of inertia of the system about an axis passing through A and parallel to DB would be :

A
$$\sqrt 3$$ ml2
B
2 ml2
C
ml2
D
3 ml2
3
JEE Main 2021 (Online) 26th February Morning Shift
+4
-1
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : Body 'P' having mass M moving with speed 'u' has head-on collision elastically with another body 'Q' having mass 'm' initially at rest. If m << M, body 'Q' will have a maximum speed equal to '2u' after collision.

Reason R : During elastic collision, the momentum and kinetic energy are both conserved.

In the light of the above statements, choose the most appropriate answer from the options given below :
A
A is correct but R is not correct.
B
A is not correct but R is correct.
C
Both A and R are correct and R is the correct explanation of A.
D
Both A and R are correct but R is NOT the correct explanation of A.
4
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
Particle A of mass m1 moving with velocity $$\left( {\sqrt3\widehat i + \widehat j} \right)m{s^{ - 1}}$$ collides with another particle B of mass m2 which is at rest initially. Let $$\overrightarrow {{V_1}}$$ and $$\overrightarrow {{V_2}}$$ be the velocities of particles A and B after collision respectively. If m1 = 2m2 and after
collision $$\overrightarrow {{V_1}} =$$$$\left( {\widehat i + \sqrt 3 \widehat j} \right)$$ , the angle between $$\overrightarrow {{V_1}}$$ and $$\overrightarrow {{V_2}}$$ is :
A
105o
B
15o
C
-45o
D
60o
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