Given:

Jet diameter, d=30 mm=0.03m

Velocity of jet V=15m/s

Weight of plat e W=245.25 N

Let h be the height of plate and OG=$\frac{h}{2}$

Due to the impact of jet, plate moves form OGA to O,G,A which makes an angle $\Theta$ from vertical force exerted by jet , F=$P.A.V^{2}$

=$p\times \frac{\pi}{4}\times (d)^{2}\times v^{2}$ $1000\times \frac{\pi}{4}\times (0.03)^{2}\times (15)^{2}$

=159.04 N

Taking moment abou the hinge 'o'

$F\times OG=w\times (OG_{1}\times sin\Theta)$

$F\times \frac{h}{2}=w\times \frac{h}{2}sin\Theta$

15904=$245.25\times sin\Theta$

$sin \Theta$=0.6485

Angle of swigng $\Theta$=40.427