(d) $\phi = NBA\cos{\theta = 10\ Ba^{2}}\cos{\omega t}$ $e = - \frac{d\phi}{dt} = - \frac{d}{dt}\left( 10\ Ba^{2}\cos{\omega t} \right) = 10\ Ba^{2}\omega\sin{\omega t}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.