A body is projected downwards at an angle of ${30}^0$ to the horizontal with a velocity of 9.8 m/sec from the top of a tower 29.4 m high. How long will it take before striking the ground?

(g=9.9 m/s²)

$\begin{array}{l}given initial velocity=u=9.8 m/s; downward angle of projection wrt horizontal=\theta ={30}^0; tower height=h=29.4m;g=9.8 m/s^2\\ vertical component of the velocity=v_y=U\sin \theta =9.8\sin {30}^{\circ }; Taking downward as +y-axis:\\ v_y=4.9\mathrm{m}/\sec \\ \text{ We know }h=U\sin \theta t+\frac{1}{2}g{t}^2 ; substitute given values,\\ \Rightarrow 29.4=4.9t+\frac{1}{2}\left(9.8\right)t^2\\ \Rightarrow t=2sec=time taken to strike the ground\end{array}$