Question

Three particles of equal masses $m$ are rigidly connected to each other by massless rods of length $\ell$ forming an equilateral triangle as shown in figure. The assembly is to be given an angular velocity $\omega$ about an axis perpendicular to the plane of triangle. For fixed $\omega$, the ratio of the kinetic energy of the assembly for an axis through B compared with that for an axis through $A$ ($A$ is centroid of the shown triangle) is equal to

• A. 3
• B. 2
• C. 1
• D. 1/3

Answer 1

The correct option is B 2

According to the concept of rotational motion,
in the given diagram moment of inertia from point "$A$" to every extreme point "$m$" is $m{l}^2$
than distance between every "$m$" to "$m$" which (point "B") will be double of initial moment of inertia,so it will be $2m{l}^2$
$\frac{K.E_B}{K.E_A}=\frac{2m{l}^2}{m{l}^2}$
$\frac{K.E_B}{K.E_A}=2$