Data : f1 = 100 rpm, m = 20 g = 20 × 10-3 kg,
r = 5 cm = 5 × 10-2 m,
I1 = Idisc = 2 × 10-4 kg.m2
The MI of the disc and blob of wax is
I2 = I1 + mr2
\
By the principle of conversation of angular momentum, I1\(\omega_1\) = I2\(\omega_2\).
![](https://www.sarthaks.com/?qa=blob&qa_blobid=14188197130070907157)
This is the new frequency of rotation.