iv). In a certain unit, the radius of gyration
of a uniform disc about its central and
transverse axis is

Its radius of
gyration about a tangent in its plane (in
the same unit) must be
(A)

(B)

(C)
![\sqrt[2]{2.5?} \sqrt[2]{2.5?}](https://tex.z-dn.net/?f=+%5Csqrt%5B2%5D%7B2.5%3F%7D+)
(D)

Answers
Answer:
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Explanation:
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Answer:
To Find :
The radius of gyration of the uniform disc about a tangent in its plane = ?
Solution :
Since we know that the moment of inertia disc about central transverse axis is given as :
= \frac{mR^2}{2}}
Here m and R are mass and radius of disc respectively .
Let , K = radius of gyration
∴ {mK^2\:= \frac{mR^2}{2}}
So, K = \frac{R}{\sqrt[2]{2}}
= 2.5 units (radius of gyration is given 2.5 units )
Now by theorem of perpendicular axis :
Ix + Iy = Iz
Where Ix , Iy and Iz are the moment of inertia about x , y and z axis .
∴For a uniform disc , Ix = II
So, Ix = Iy = \frac{mR^2}{2\times 2}
= \frac{mR^2}{4}
Now by theorem of parallel axis :
Moment of inertia about tangent =
{\frac{mR^2}{4} \:+\:{mR^2}}
= \frac{5mR^2}{4}
Let K' be the radius of gyration about the tangent , then :
mK'² = \frac{5mR^2}{4}
So, K' = \frac{\sqrt[5]{R}}{2}
Since \frac{R}{\sqrt[2]{2}}
=2.5 units
So, K' = {\frac{\sqrt[2]{5}}{\sqrt[2]{2}}\:×\:2.5}
= √12.5 units
Hence , radius of gyration about a tangent of the disc is
= √12.5 units
Explanation: