
$\mathrm{F}_{1}+\frac{\mathrm{mv}_{1}^{2}}{\mathrm{R}} \cos \theta=\mathrm{mg} \sin \theta$
$\frac{\mathrm{mv}_{2}^{2}}{\mathrm{R}} \cos \theta=\mathrm{mg} \sin \theta+\mathrm{F}_{2}$
$\mathrm{F}_{1}=\mathrm{F}_{2} \mathrm{given}$
$\mathrm{g} \sin \theta-\frac{\mathrm{v}_{1}^{2}}{\mathrm{R}} \cos \theta=\frac{\mathrm{v}_{2}^{2}}{\mathrm{R}} \cos \theta-\mathrm{g} \sin \theta$
$\tan \theta=\frac{\mathrm{v}_{2}^{2}+\mathrm{v}_{1}^{2}}{2 \mathrm{gR}}=\frac{100+400}{2 \times \mathrm{g} \times 1000}=\frac{1}{4 \mathrm{g}}$