A square shaped coil of area $70 \mathrm{~cm}^{2}$ having 600 turns rotates in a magnetic field of $0.4 ~\mathrm{wbm}^{-2}$, about an axis which is parallel to one of the side of the coil and perpendicular to the direction of field. If the coil completes 500 revolution in a minute, the instantaneous emf when the plane of the coil is inclined at $60^{\circ}$ with the field, will be ____________ V. (Take $\pi=\frac{22}{7}$)