Answer to Question #286951 in Physics for Dhanush

Question

A 200-gram ball, m1 and a 100-gram ball, m2, connected by a rod with length of

60 cm. Ignore rod’s mass. The axis of rotation located at ball m2. What is the

moment of inertia of the balls? Ignore rod’s mass

Answer 1

The moment of inertia of the second ball is zero because it's at the axis of rotation. The moment of inertia of the first mass is the moment of inertia of the entire system and equals

$$I=m_1r^2=0.2·0.6^2=0.072\text{ kg}·\text m^2.$$