(c) $v = \omega\sqrt{a^{2} - y^{2}} \Rightarrow 10 = \omega\sqrt{a^{2} - (4)^{2}}\ $and$\ 8 = \omega\sqrt{a^{2} - (5)^{2}}$ On solving $\omega = 2 \Rightarrow \omega = \frac{2\pi}{T} = 2 \Rightarrow T = \pi s$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.