# Doubt from rotational mechanics

\displaystyle dL=L_f-L_i=L=\int_0^t \tau dt
\displaystyle (R+r) \int_0^t 2t dt=(R+r)t^2

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@Gaurav_2020_3 I think you have marked the point Of incorrectly.

Bro take that as O' Didn't see that O is the centre given and we conserve angular momentum about that point