Question

Two point like spheres of mass $5kg$ are joined by $1m$ long weightless rod. The $M.I.$ in $kg$. $m^2$ unit about an axis perpendicular to the rod and through the center of any of the sphere will be (in kg-$m^2)$-

• A. 10
• B. 2.5
• C. 5
• D. 1

Answer 1

The correct option is C 5

REF.Image.

Point line spheres $\Rightarrow$ moment or inertia

of sphere -1 will be zero because its

point line so where mass will be

at the axis of rotation so

$r=0\Rightarrow I_1=0$ for sphere -2

That of sphere -2 about axis passing

through sphere -1 will be

$I_2=m_2{r}^2=5\times 1^2=5kg{m}^2$

Net $I=I_1+I_2=0+5=5kg{m}^2$