Q.

The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is 2400g cm2. The length of the 400 g rod is nearly    [2024]
 

1 8.5 cm  
2 17.5 cm  
3 20.7 cm  
4 72.0 cm  

Ans.

(1)

Moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod

            Icm=Ml212                                                     ...(i)

where, M = Mass of the rod, l = Length of the rod

Given, M=400g, l=?, Icm=2400g cm2

From eq (i), l=Icm×12M=2400×12400=8.4848.5cm