1
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
Moment of inertia of a body about a given axis is 1.5 kg m2. Initially the body is at rest. In order to produce a rotational kinetic energy of 1200 J, the angular accleration of 20 rad/s2 must be applied about the axis for a duration of :-
A
2.5 s
B
3 s
C
5s
D
2 s
2
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
A thin smooth rod of length L and mass M is rotating freely with angular speed $$\omega$$0 about an axis perpendicular to the rod and passing through its center. Two beads of mass m and negligible size are at the center of the rod initially. The beads are free to slide along the rod. The angular speed of the system , when the beads reach the opposite ends of the rod, will be :-
A
$${{M{\omega _0}} \over {M + 3m}}$$
B
$${{M{\omega _0}} \over {M + m}}$$
C
$${{M{\omega _0}} \over {M + 6m}}$$
D
$${{M{\omega _0}} \over {M + 2m}}$$
3
JEE Main 2019 (Online) 9th April Morning Slot
+4
-1
The following bodies are made to roll up (without slipping) the same inclined plane from a horizontal plane. : (i) a ring of radius R, (ii) a solid cylinder of radius R/2 and (iii) a solid sphere of radius R/4 . If in each case, the speed of the centre of mass at the bottom of the incline is same, the ratio of the maximum heights they climb is :
A
20 : 15 : 14
B
4 : 3 : 2
C
2 : 3 : 4
D
10 : 15 : 7
4
JEE Main 2019 (Online) 9th April Morning Slot
+4
-1
A stationary horizontal disc is free to rotate about its axis. When a torque is applied on it, its kinetic energy as a function of $$\theta$$, where $$\theta$$ is the angle by which it has rotated, is given as k$$\theta$$2. If its moment of inertia is I then the angular acceleration of the disc is :
A
$${k \over {4I}}\theta$$
B
$${k \over {I}}\theta$$
C
$${k \over {2I}}\theta$$
D
$${2k \over {I}}\theta$$
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