Question

In rectangle $ABCD$, $AB=2l$ and $BC=l$. Axes $xx$ and $yy$ pass through the centre of the rectangle. The moment of inertial is least about

• A. $DB$
• B. $BC$
• C. $x{x}^{\prime }$
• D. $y{y}^{\prime }$

Answer 1

The correct option is C $x{x}^{\prime }$

Moment of inertia is least about an axis which passes through COM and the distribution is such that the more mass is away from the axis. If we take yy' the distance between yy' and BC is l whereas for xx' its distance to AB is l/2. thus, more mass is distributed closer to xx' than yy', and hence its moment of inertia is minimum about xx'