Question

Three identical balls with masses of M, 2M, and 3M are fastened to a massless rod of length L as shown. The rotational inertia about the left end of the rod is ?

Please help. Thank you

Answer 1

We know that

$I=mr^2$

$I=I_1+I_2+I_3$

$$I=(3M)\times0^2+2M\times(\frac{L}{2})^2+ML^2$$

$I=\frac{3}{2}ML^2$