Rotational Motion Question 70
Question: A thin circular ring of mass M and radius r is rotating about its axis with constant angular velocity $ \omega $ . Two objects each of mass m are attached gently to the opposite ends of a diameter of the ring. The ring now rotates with angular velocity given by
[AIPMT (M) 2010]
Options:
A) $ \frac{(M+2m)\omega }{2m} $
B) $ \frac{(M+2m)\omega }{2m} $
C) $ \frac{(M+2m)\omega }{M} $
D) $ \frac{M\omega }{M+2m} $
Show Answer
Answer:
Correct Answer: D
Solution:
In the absence of external torque, angular momentum remain constant
$ L=I\omega =I’\omega ’ $
$ \therefore $ $ MR^{2}\omega =(M+2m)R^{2}\omega ’ $
$ \omega ‘=\frac{M\omega }{(M+2m)} $
