1
JEE Main 2019 (Online) 10th April Evening Slot
+4
-1
A solid sphere of mass M and radius R is divided into two unequal parts. The first part has a mass of $${{7M} \over 8}$$ and is converted into a uniform disc of radius 2R. The second part is converted into a uniform solid sphere. Let I1 be the moment of inertia of the disc about its axis and I2 be the moment of inertia of the new sphere about its axis. The ratio I1/I2 is given by :
A
65
B
140
C
185
D
285
2
JEE Main 2019 (Online) 10th April Evening Slot
+4
-1
The time dependence of the position of a particle of mass m = 2 is given by $$\overrightarrow r \left( t \right) = 2t\widehat i - 3{t^2}\widehat j$$ . Its angular momentum, with respect to the origin, at time t = 2 is
A
36 $$\widehat k$$
B
- 48 $$\widehat k$$
C
$$- 34\left( {\widehat k - \widehat i} \right)$$
D
$$48\left( {\widehat i + \widehat j} \right)$$
3
JEE Main 2019 (Online) 10th April Morning Slot
+4
-1
A thin disc of mass M and radius R has mass per unit area $$\sigma$$(r) = kr2 where r is the distance from its centre. Its moment of inertia about an axis going through its centre of mass and perpendicular to its plane is :
A
$${{M{R^2}} \over 3}$$
B
$${{M{R^2}} \over 6}$$
C
$${{2M{R^2}} \over 3}$$
D
$${{M{R^2}} \over 2}$$
4
JEE Main 2019 (Online) 10th April Morning Slot
+4
-1
Two coaxial discs, having moments of inertia I1 and I1/2, are rotating with respective angular velocities $$\omega$$1 and $$\omega$$1/2 , about their common axis. They are brought in contact with each other and thereafter they rotate with a common angular velocity. If Ef and Ei are the final and initial total energies, then (Ef - Ei) is:
A
$${{{I_1}\omega _1^2} \over {24}}$$
B
$${{{I_1}\omega _1^2} \over {12}}$$
C
$${3 \over 8}{I_1}\omega _1^2$$
D
$${{{I_1}\omega _1^2} \over {6}}$$
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