Question

A turn table having moment of inertia $10kg-m^2$ rotates at a constant rate of $120rpm$. If a block is placed such that the new moment of inertia of the system is $20kg-m^2$, the new angular speed of the system is

• A. $4\pi rad/s^2$
• B. $2\pi rad/s^2$
• C. $120rad/s^2$
• D. $60rad/s^2$

Answer 1

The correct option is B $2\pi rad/s^2$

By conservation of angular momentum,
$I_1{\omega }_1=I_2{\omega }_2$