JEE Mains · Physics · STD 11 - System of particles and rotational motion
- JEE Mains 2021
- Medium
- MCQ
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 \(I_{x}, I_{y}\) and \({I}_{z}\) 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 :
Pick an option to check your answer.
Answer & Solution
Correct Answer
(B) \(A\) is not correct but \(R\) is correct.
Step-by-step Solution
Detailed explanation
\(I_{z}=I_{x}+I_{y}\) (using perpendicular axls theorem)
\(l = mk ^{2}\) (K: radius of gyratlon)
so \(m K_{z}^{2}=m K_{x}^{2}+m K_{y}^{2}\)
\(K_{z}^{2}=K_{x}^{2}+K_{y}^{2}\)
so radius of gyration about axes \(x, y\) and \(z\) won't be same hense asseration \(A\) is not correct reason \(R\) is correct statement (property of a rlgid body)
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