Question

The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is 2400 g cm². The length of the 400 g rod is nearly ______.

Options

• 20.7 cm

• 72.0 cm

• 8.5 cm

• 17.5 cm

Answer 1

The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is 2400 g cm². The length of the 400 g rod is nearly 8.5 cm.

Explanation:

The moment of inertia of a thin rod about an axis that traverses its midpoint and is perpendicular to the rod is:

`(ML^2)/12` = 2400

⇒ L² = `(12 xx 2400)/40`

⇒ L² = `sqrt 72`

⇒ L = 8.5 cm