- Exam
- JEE Main
- Year
- 2021
- Date
- 25 July
- Shift
- Morning Shift
- Subject
- Physics
- Chapter
- Rotational Motion
JEE Main 2021 · 25 July · Morning Shift · Physics · Rotational Motion
Given below are two statements: one is labelled as Assertion A and...
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 and radius about axes (passing through its plane) and Z-axis which is perpendicular to its plane were found to be and , respectively. The respective 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:
Options
- ABoth A and R are correct but R is not the correct explanation of A.
- BA is not correct but R is correct.
- CA is correct but R is not correct.
- DBoth A and R are correct and R is the correct
explanation of A.
Correct answer
B. A is not correct but R is correct.
Step-by-step solution
(using perpendicular axis theorem)
and radius of gyration)
so
So radius of gyration about axes and will not be same, hence assertion A is not correct reason R is correct statement (property of a rigid body).