(c) $v_{\max} = 100 = a\ \omega;$ $\omega = \frac{100}{a} = \frac{100}{10} = 10\ rads^{- 1}.$ $v^{2} = \omega^{2}(a^{2} - y^{2})$ or $50^{2} = 10^{2}\left( 10^{2} - y^{2} \right)$ or $25 = 100 - y^{2}$ or $y = \sqrt{75} = 5\sqrt{3}\ cm$.
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.