Question

14 The radius of gyration of a body about an axis &ta

distance 6 cm from its centre of mass is 10 cm.
Then, its radius of gyration about a parallel axis
through its centre of mass will be
(a) 80 cm (b) 8 cm (c) 0.8 cm (d) 0.08 cm

Answer 1

Correct option is B 8 cm.

Let radius of gyration for the axis not passing through center of mass be r and that for the axis passing through the center of mass be k and the distance between the two parallel axes be a.

Parallel axes theorem gives:

`{mr}^(2) = m( {k}^(2) + {a}^(2) ) \\ ⇒ {r}^(2) = {k}^(2) + a {}^(2)`

`⇒k = \sqrt{ {10}^(2) - {6}^(2) } = 8cm.`

Thus, option B is the correct answer.