1
JEE Main 2021 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : Moment of inertia of a circular disc of mass 'M' and radius 'R' about X, Y axes (passing through its plane) and Z-axis which is perpendicular to its plane were found to be Ix, Iy and Iz respectively. The respectively radii of gyration about all the three axes will be the same.

Reason R : A rigid body making rotational motion has fixed mass and shape. In the light of the above statements, choose the most appropriate answer from the options given below :
A
Both A and R are correct but R is NOT the correct explanation of A.
B
A is not correct but R is correct.
C
A is correct but R is not correct.
D
Both A and R are correct and R is the correct explanation of A.
2
JEE Main 2021 (Online) 22th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Consider a situation in which a ring, a solid cylinder and a solid sphere roll down on the same inclined plane without slipping. Assume that they start rolling from rest and having identical diameter.

The correct statement for this situation is
A
All of them will have same velocity.
B
The ring has greatest and the cylinder has the least velocity of the centre of mass at the bottom of the inclined plane.
C
The sphere has the greatest and the ring has the least velocity of the centre of mass at the bottom of the inclined plane.
D
The cylinder has the greatest and the sphere has the least velocity of the centre of mass at the bottom of the inclined plane.
3
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
A body rolls down an inclined plane without slipping. The kinetic energy of rotation is 50% of its translational kinetic energy. The body is :
A
Solid sphere
B
Solid cylinder
C
Hollow cylinder
D
Ring
4
JEE Main 2021 (Online) 18th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Consider a uniform wire of mass M and length L. It is bent into a semicircle. Its moment of inertia about a line perpendicular to the plane of the wire passing through the center is :
A
$${1 \over 4}{{M{L^2}} \over {{\pi ^2}}}$$
B
$${1 \over 2}{{M{L^2}} \over {{\pi ^2}}}$$
C
$${2 \over 5}{{M{L^2}} \over {{\pi ^2}}}$$
D
$${{M{L^2}} \over {{\pi ^2}}}$$
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