Đáp án:
Ta có \(v = \omega R\)
\({R_A} = {R_B} + AB = {R_B} + 20\)
\( \Rightarrow \dfrac{{{v_A}}}{{{v_B}}} = \dfrac{{{R_A}}}{{{R_B}}} \Leftrightarrow \dfrac{{50}}{{10}} = \dfrac{{{R_B} + 20}}{{{R_B}}} \Rightarrow {R_B} = 5cm\)
Vậy \(\omega = \dfrac{{{v_B}}}{{{R_B}}} = \dfrac{{10}}{5} = 2rad/s\)